The series follows a polite 4-year old boy named Kotaro, who moves into an apartment building all by himself. He quickly befriends the other inhabitants — a young woman named Mizuki Akitomo, the rather eccentric Isamu Tamaru, and especially his next-door neighbor and struggling manga artist named Shin Karino. As the series progresses, Kotaro's life and how he ended up living like this slowly becomes clear.
The manga was adapted into a ten-episode live-action television drama broadcast on TV Asahi in 2021, and a ten-episode anime adaptation by Liden Films which debuted worldwide on Netflix in March 2022. Each episode of the anime consists of multiple smaller stories.
Tropes:
- Abusive Parents: While Kotaro experienced Parental Neglect from his mother, it was his father that was frequently abusive to both his son and his then-wife. Flashbacks often show him yelling at his family and thrashing the house, with the mother often the target of his violent episodes or shielding Kotaro from them. Kotaro currently lives alone because he cannot find his mother and knows better than to go back to his father just yet (even though he still loves him and hopes to reunite with him). The father is still trying to find his son and is implied to only be interested in his ex-wife's money.
- Adapted Out: Takei is absent from the live-action series and her trait of disliking children is passed on to Kobayashi.
- Adaptational Nice Guy: Kotaro's father is depicted more sympathetically in the live-action series than the manga, with more self-restraint and a better relationship with his wife when she was pregnant with Kotaro.
- Adorably Precocious Child: Not only can Kotaro can handle living on his own surprisingly well, but he's incredibly perceptive about how other people act and he can easily tell what they are really thinking about. Although often weirded out as well, many adults are charmed by his unexpected mature side and find it endearing. However, he's still a child underneath, and a lot of his maturity comes from the way his childish mind has interpreted what he's lived through, including his necessity of being seen as strong.
- He ocasionally lets his more age-appropiate side show, like when Karino's boss gave him a tour of the building and Kotao was completely unable to hide his fascination, specially when he showed him a Tonosaman arcade machine.
- Amicable Exes: Akane is Karino's ex-girlfriend, but the two are on friendly terms to the point that she'll spontaneously stay at his house without issue whenever she has a fight with her boyfriend. Akane still shows enough concern for her ex that she insists on taking over his guardian duties for Kotaro when he has a major manga deadline to meet.
- Anger Born of Worry: When Kotaro helps a friend of his to run away from home, he ends up reflecting that he has nobody to worry for him if he ran away from home. When he broods over this in his apartment, Karino barges inside upset because he couldn't find him anywhere for their usual visit to the bath house. This seems to make Kotaro happy, and he gives Karino a sincere apology (which the latter finds out of character for him.)
- Antiquated Linguistics: Kotaro talks like a samurai, since his role model is the samurai character Tonosaman. The character uses olden Japanese language, such as the first-person pronoun warawa which is historically used by female nobility. He developed this way of speaking due to watching Tonosaman as a way to cope with neglect late at night while he lived with his mother.
- Bathtub Bonding: Karino and Kotaro are frequently shown conversing with one another at the bathhouse, whether it be casual talks about their day or giving advice, and it contributes to the close friendship they develop.
- Big Eater: Deconstructed. Kotaro is sometimes shown eating food proportions large enough to feed multiple people — however each time it's revealed to be due to some disturbing reason concerning his circumstances or background and not because of a big appetite.
- He cooks himself meals at home that could feed a few people, much to his neighbours' surprise. Rather than to satiate his hunger, it turns out to be a way for him to cope with loneliness by pretending all his dishes are his friends.
- Kotaro at one point gains weight, and Takei finds out it's because he's been eating his classmate's leftovers that they dump on him. This saddens her and the adults watching him as it's clear he's eating the leftovers not out of hunger but simply because he hates the idea of wasting food due to his previous experience of going hungry from neglect. His teacher resolves not to let the other kids give him leftovers anymore for his health's sake.
- In one chapter he repeatedly insists on tackling a kids challenge at a family restaurant where he tries (and fails) to finish a humongous serving of omurice. Uda finds out that Kotaro is not interested in the meal itself and only does it because he hallucinates his mother's voice when he gets too full and yearns to keep hearing it so that he doesn't forget her voice.
- Bitter Sweet Ending: The anime ends on a partially bleak but otherwise hopeful note, with more emphasis on sweet than bitter. The final story of the last episode has Karino discovering that Kotaro's mother has died, and he resolves to keep it a secret despite knowing Kotaro will find out one day and may end up hating him for it. Despite this depressing revelation and its implications, this gets balanced out with the two of them returning home with Tamaru and Takei and the four of them hanging out with each other and their many companions at Kotaro's place, reinforcing that Kotaro will live a more happy life from now on. An uplifting montage shows how the other characters they've met through the season are doing (such as Mizuki and the three abandoned siblings doing okay for themselves), and it ends on a still image of Kotaro's friends, child, and adult alike (with some implication Tamaru finally gets to spend time with his son) at his apartment.
- But Now I Must Go: Mizuki eventually leaves the apartment complex for safety precautions because her ex-boyfriend becomes violent after she breaks up with him and there isn't enough evidence to have him arrested.
- The Cameo: Ayaka "A-rin" Sasaki of Momoiro Clover Z appears in the live-action series as a maid at the real-life Maid Cafe Maidreamin (she and the cafe chain share the same pink signature color). She is a groupmate of Kanako Momota, who plays the lawyer Ayano Kobayashi.
- Child Hater:
- A newer resident of the Shimizu apartments, Takei, is a woman who can't handle children but tries to hide it since she knows women get harshly judged by society for it. She feels obliged to help take care of Kotaro alongside her neighbours nevertheless (even though she clearly stresses out when doing so), and he hangs out with her to help her overcome her discomfort.
- In the live-action, Kobayashi is a Composite Character of her original manga self and Takei, so she inherits the latter's discomfort with children as an Informed Flaw.
- Companion Cube: Kotaro once tricks a man handing out balloons into giving him four instead of just one. Then he proceeds to draw faces on them, labels them "mom", "dad", "brother" and "sister", and takes them with him to the playground. The man eventually discovers the deception, but when he sees what Kotaro did to the balloons, he quietly leaves him alone and even hopes for Kotaro the balloons will last a long time.
- Cruel to Be Kind: When Tamaru's biological child shows up to spend time with his dad, the man takes on a serious demeanor and orders him to go back home to his mother. The reason for that is because the boy went behind his mother's back to find his father's address and ran away to meet him in secret. If Tamaru were to openly embrace him or shower him with love, then he'd only be encouraging that type of rebellious behavior.
- Cuteness Proximity: Tamaru's usual demeanor is that of a yakuza, being rude and easy to threaten violence on anyone who dares look at him the wrong way. When he approaches Kotaro, however, he absolutely melts, keeps affectionately calling him Kotaro-kun ("widdle Kotaro" in the official Netflix translation) and tries to hug him or rub his cheeks (which Kotaro usually has to stop using his toy sword).
- The Dentist Episode: Multiple stories take place at the dentist.
- One chapter (part of Episode 9 in the anime) revolves around Kotaro visiting his dentist, who takes the opportunity to not just check his teeth but also make sure the boy is safe and healthy. This is due to a previous incident where he missed the warning signs about a little girl with poor teeth health and found out in the news that she was neglected by her mother.
- Kotaro scolds Karino for not going to the dentist to remove his wisdom teeth, only to reveal he has a loose tooth and has also been avoiding going to the dentist. Both end up going to Kotaro's usual dentist to get themselves checked out. Here, Kotaro learns the meaning behind the Japanese word for wisdom teeth (which translates literally to "parents don't know") and worries about his own parents not being alive by the time he gets his removed.
- Dirty Kid: Whenever Kotaro makes innocent remarks about women that can come off as pervy, such as saying what he thinks about Mizuki's or any other woman's scent or how he makes other adult women do things with him, Karino accuses him of actually being pretty dirty-minded.
- Dysfunction Junction: The apartments' various residents either deal with parental alienation (Tamaru) and domestic violence (Mizuki) or have parental abuse as backstory (Kotaro, Takei, and Aota). Uda is the most well-adjusted of the group but is linked to Kotaro's family issues and so deals with his complex feelings towards them (such as secretly feeling guilty for being the one to report Kotaro's father to the police and separating him from Kotaro as a result). Even the relatively-together Karino has been shaped by his orphanhood from a young age and is revealed to have some tension with the aunt that became his guardian. An absurd amount of side-characters also have familial issues.
- Face of a Thug: It's unknown what Tamaru's occupation is, but he looks and carries himself like a low-level yakuza member. His frightening face and appearance is to the point that the parents at kindergarten are either afraid or judgemental of him and multiple authority figures approach him whenever he looks suspicious hanging out with Kotaro.
- Fun with Homophones: When Karino informs him that the apartments have no bathtubs and the occupants go to the nearby bath house (銭湯 sentou), Kotaro thinks that they have to go to battle (戦闘 sentou) to get a bath.
- Furo Scene: The anime has several bath scenes, mostly when Kotaro and Karino go to the local bath house and talk about various things with each other.
- Gossipy Hens: A group of women (often found in the kindergarten) can be heard gossiping about a certain character and their circumstances. This is what allows Kotaro, Karino and the other protagonists to gain a better understanding of a character's past or living situation.
- Happy Flashback: In the story where Kotaro does his "umbrella service" for people at the train station during the rainy period, he remembers his father protecting him with an umbrella during a walk and teaching him how to hold it for other people. This is one of the only happy flashbacks of Kotaro with his parents that's shown in the series and the first time (out of very few moments) the father is portrayed warmly and devoid of his abusive traits.
- Heel–Face Turn: Private investigator Aota temporarily moves into the apartments with the intention of confirming Kotaro's whereabouts and reporting back to his father. However he comes to genuinely befriend Kotaro, and when the latter reveals he already figured out what the man's motives were and begs him to not tell his father until he's ready Aota decides to give the father false information so that Kotaro can be left alone. By the time he leaves the apartment, he's on good terms with everyone and he's genuinely touched by Kotaro's goodbye party and present for him.
- Hollywood Tone-Deaf: Kotaro is frequently commented on for his tone-deafness. In the anime when he sings two songs (the Tonosaman theme and "Happy Birthday"), he murders them due to being off-key to a comical degree.
- Hopeless Suitor: Downplayed. Karino has a crush on Mizuki but has never openly expressed his feelings to her. That said, Mizuki has no interest in him and is quick to criticize him when the opportunity calls for it.
- Host Club: Mizuki works as a hostess, and the hostess club she works at is sometimes shown. One story has Kotaro continuously showing up to her work to request for her; the hostesses coo over him, and later Mizuki shouts him and Karino out and lets them stay at the place to enjoy themselves (although she regrets it when overhears them commenting on the hostesses' looks).
- Hypocritical Humour: When Karino surprises Akane by turning up to Kotaro's kindergarten concert, she expresses annoyance at her ex lying to her and being sneaky since she assumed he was going to be at home finishing his manga. Karino snarks back with, "Pot meet kettle," referring to Akane having just lied to him the past week by hiding a flyer about the concert from him and trying to keep him away from Kotaro.
- I Just Want to Be Loved: Kotaro gets quietly emotional whenever someone gives him the type of affection (verbal, at least) that he missed out from his parents, showing that he still yearns for that familial love.
- Innocent Prodigy: While Kotaro is smart and mature enough to take care of himself, there are plenty of moments that reinforce that he is still a young child who doesn't fully know how the world works.
- Intergenerational Friendship: Out of everyone in the apartment, Kotaro feels closest to Karino who is old enough to be his dad. Kotaro regularly goes to his neighbor for small things like borrowing his TV, and Karino often does his best to a dependable adult figure to the boy.
- Is That Cute Kid Yours?: Early on, Karino and Kotaro are frequently mistaken as father and son when they're together at a store. Karino briefly wonders if the latter could actually be his son due to a past relationship he had. Kotaro sets the record straight by saying he shares no blood ties to him.
- Jerkass to One: Kotaro is courteous to everyone and at worst expresses mild annoyance (such as when Tamaru's affections are too much for him). The one exception is Uda, who had some sort of relationship with Kotaro's mother Sayori back when she and her son lived with her ex-husband. Kotaro has a poor opinion of him as a result, and so usually hisses at him and rudely talks to him (such as giving him the derogatory nickname "the man who seduced my mother"). Although Kotaro acknowledges the man's kindness and their relationship improves over time, he still expresses disgust whenever Uda tries to so much as talk to him let alone hang out with him.
- Kid Samurai: Kotaro likes to copy his favourite show Tonosaman and evoke an image of a child samurai like the titular character, by carrying around a small toy katana and talking like a feudal Japanese lord.
- Like Father, Like Son: Tamaru's child is starting to take after his old man by styling his hair in an outrageous fashion, wearing flashy clothes and talking like a gangster.
- Loophole Abuse: The apartment building has a rule against renters with children moving in. The landlords nevertheless accept Kotaro because he himself is the renter and has no other children living with him, so he is technically not breaking this rule.
- Lying to Protect Your Feelings: It's hinted and eventually confirmed to the audience that Kotaro's mother is no longer alive. Not wanting Kotaro to be burdened with this knowledge, the adults aware of this secret make an effort to hide the truth from him so that he can go about his childhood happily and still have hope. Kobayashi and her law firm disguise the payments from his mother's life insurance as a weekly allowance from a generous donor, Aota makes Uda promise to not reveal the truth to Kotaro, and Karino goes out of his way to hide the mother's name from Kotaro at her family grave and resolves to accompany him there from now on so that he can keep doing the same.
- Maid Cafe: Kotaro visits a maid cafe in the manga and live-action series. He doesn't really seem to enjoy it, but he only goes there to hear somebody bid him "welcome home", which the maids customarily do as in real life. After learning of this, Karino does the same to him.
- Minor Living Alone: The entire premise of the story is that Kotaro is only four years old (later five) yet already lives on his own in an apartment.
- Mistaken for Pedophile: Due to the yakuza-like way he dresses and how chummily he acts around Kotaro, Isamu Tamaru is regarded with suspicion whenever the two of them are together, like people gossiping behind his back. During a shopping trip, both a security guard and a police officer question him about what he is doing with Kotaro.
- Mood Whiplash: One episode has Mizuki trying her darnest to take Kotaro's photo which leads to him doing everything to keep his face hidden through comical means. Then it cuts to a flashback that shows Kotaro's father violently demanding that the orphanage return his son after he found him through an online photo, thus explaining his disdain for getting his photo taken.
- Neat Freak: Kotaro insists on bathing every day. Earlier in the story he freaks out when the bathhouse is closed due to a broken boiler, and fears his usual bathhouse companion Karino will hate him now that he can't bathe for a day. He eventually resorts to washing himself in the sink.
- Never Had a Birthday Party: Kotaro's neighbors are shocked when they learn the boy had no idea birthdays are a reason for celebration and thus never had a party for his. When they decide to give him a proper birthday party, Kotaro of course takes this very seriously, and even starts practicing his lung capacity for the moment he has to blow out the candles on his birthday cake. He later shares his cake, many candles, and his birthday itself with the neighborhood cats, who he assumes have also never had their birthday celebrated.
- Not So Stoic: Karino is usually very soft-spoken and has a blank look on his face, but he sometimes loses his composure towards Kotaro which is typically in a way that shows he cares.
- O.O.C. Is Serious Business: Given how polite and composed Kotaro is, his neighbors are understandably shocked when they meet Uda for the first time and see the child furiously charging at him and trying to attack him. They learn it's because they already know each other, and Kotaro considers him his father's enemy due to the man apparently seducing his mother.
- Parental Neglect: Kotaro's mother was highly neglectful of her son when she took care of him by herself. This is strongly implied to be due to her own depression and inability to take care of herself, as she often blamed herself for not being a good enough mother and still clearly felt some concern and guilt towards Kotaro despite her unwillingness to engage with him. It reached a point where she sometimes considered leaving him somewhere, and she eventually did abandon him at home while asking him to continue living even if she never comes back. It is hinted and eventually confirmed that his mom has already passed away without Kotaro's knowledge, with the latter now receiving money from her life insurance and Karino finding her name on her family grave.
- Parental Substitute: While he mostly acts as Kotaro's friend and neighbor, Karino occasionally steps into a fatherly role when the child needs an adult, like during parent conversations at school.
- Poverty Food: It's greatly implied that Kotaro used to eat tissues when he was younger just to sate his hunger. Karino is greatly disturbed when he realizes why Kotaro is so picky with tissues and when he remarks that it tastes sweet.
- Private Detective: A man named Aota temporarily moves into the apartment building and quickly befriends Kotaro, but it turns out he is a private detective hired by Kotaro's father to find his son. Fortunately for Kotaro, Aoto sympathizes with the boy and gives Kotaro's father a fake address. He stays around for a while afterwards.
- Raised by the Community: The Shimizu apartment residents take care of Kotaro together by accompanying him to and from his kindergarten and escorting him to certain locations that are too far for him by himself.
- Replacement Goldfish: Defied. The main reason Tamaru is so affectionate towards Kotaro is because of his current separation from his wife and how he's unable to see their son. Kotaro is aware of his situation and refuses to be used as a replacement for Tamaru to exploit.
- The Reveal: Chapter 137 gives a shocking reveal that Kotaro's mother Sayori used to live at the Shimizu apartment and and was neighbours with Karino, who left a positive impression on her from the few heartfelt and encouraging interactions they had. Not only does this give a glimpse of what Sayori was doing in between abandoning her son and her death, but the revelation that Karino actually (unknowingly) already met her puts his interactions with Kotaro (and his determination to watch over him in her place) into a whole new perspective.
- Rose-Haired Sweetie: Mizuki has bright pink hair and a sweet demeanor. She's immediately establishes a bond with Kotaro and often does her best to help him. She offers to help Kotaro sleep at night once she realizes the boy is having nightmares and offers to accompany him to the bathhouse.
- Rules of Orphan Economics: Kotaro receives a weekly allowance from his mother's life insurance. The exact sum is never stated, but it's obviously enough for him to pay his rent and food.
- The Runaway: Kotaro's friend Takuya decides to run away from home and invites Kotaro’s to join him. They don't get too far since Takuya is afraid to actually leave his neighborhood, and he changes his mind completely when he goes to Kotaro's place and learns that the latter is living all alone.
- Running Gag: It's a recurring joke for Karino to tag along or show up and get told that he wasn't invited. Sometimes it's out of responsibility, such as not letting Kotaro walk at night or long distances alone. Other times there is one or more adult present and Karino simply shows up to not be left out.
- Shout-Out: The story of Momotarō is brought up when Kotaro learns the woman who runs the local supermarket is pregnant but doesn't understand the concept since he thought babies were born from peaches.
- Show Within a Show: Kotaro's favorite show is the anime Tonosaman and he models himself after the titular feudal lord character, to the point of carrying a toy katana around. The name is a wordplay between feudal lord (殿様 tonosama) and "man". It's noted to not be a particularly popular show, but Kotaro loves it anyway.
- Sick Episode: One chapter has Kotaro running a fever after helping out a sickly classmate. He refuses to go home since he thinks being sick as being weak. He changes his mind after his sickly classmate explains that he doesn't want to infect others with his sickness.
- Sleepwalking: Kotaro is shown to sometimes experience sleep-walking episodes, which is due to childhood stress.
- Social Services Does Not Exist: Zig-zagged with Kotaro and the other neglected children that appear. Some people are aware that Kotaro lives all by himself, and a legal firm monitors him and provides him money so that he can financially support himself. Yet, while they are certainly helpful towards him, none ever seem to consider calling child protection services or have Kotaro placed in foster care or an orphanage. His backstory reveals that he did briefly live in an orphanage after his mother abandoned him, but he left after his father discovered his whereabouts and caused a scene when tried to forcibly take him back. One story however does show Kotaro meeting three siblings who have likewise been abandoned by their parents, but they are not as independent as him and are eventually taken away by child protection services.
- Spin-Off: Hanawa is a supporting character and Kotaro's teacher in the live-action drama, and he stars in his own spin-off series titled Hanawa-sensei is Incompetent!? (花輪せんせいは半人前!?) that aired concurrently with the parent series.
- Spotting the Thread: Uda discovers that someone is masquerading as Kotaro's mother when a social media account under her name tries to contact him and other friends of Kotaro. The child doesn't notice when he catches sight of this account and he immediately makes his own account to talk to her. He falls for it at first and happily converses with her — however, he realizes it's all a ruse when "Sayori" expresses surprise at his feudal speech mannerisms because he knows she's familiar with the way he currently talks. He correctly identifies the person behind her account to be his father, since Kotaro only developed that way of speaking after he and his mother were separated from him.
- Starving Artist: Downplayed. Karino is able to afford an apartment and basic needs like food, but he is not a very successful manga artist and has had his fair share of financial struggles in life.
- Stepford Smiler: The usually stoic Kotaro surprises his classmates when he shows he's capable of giving a bright smile for the "Smiling Sun" role in their play. He reveals to his teacher that he can fake a smile convincingly because he would do it to hide his troubles in the past, and he correctly suspects that his teacher has been doing the same thing.
- Taking Advantage of Generosity: Kotaro reunites with an old friend from his orphanage, Tasuku, whom he idolizes. He quickly charms the boy and gets Kotaro to give him huge sums of money from his weekly allowance, supposedly so they can buy a house together. Both Karino and Kobayashi get suspicious, however, and when Kobayashi does a background check on Tasuku, she finds out he has debts to multiple people and is actually using Kotaro's money to pay them off. Karino and Kobayashi both confront Tasuku and try to tell Kotaro the truth, but ultimately the latter reveals he knew all along his friend was deceiving him but wanted to give him a chance to do the right thing. It is Kotaro's belief in him that ultimately makes Tasuku do a Heel–Face Turn and find a job as a construction worker so he can pay back Kotaro the money he got from him.
- The Stoic: Kotaro rarely shows any emotion or pain, and considers doing so as a weakness.
- This Is a Work of Fiction: In the first few minutes of each live-action episode, a disclaimer is displayed on an in-universe surface to state the work is fictional.
- Troubled Abuser: It's implied Kotaro's mother was going through some serious mental health issues that led to her neglect of Kotaro.
- Troubling Unchildlike Behavior: Downplayed. Kotaro acts incredibly mature for his age, especially when interacting with other children, and frequently demonstrates a disturbingly good understanding of complex situations like abuse. He is so mature that the adults around him worry about his state since catch on that he acts this way due to Parental Neglect and would prefer him to act like a child.
- Trying Not to Cry: Kotaro outright states that he doesn't like crying and remains pretty stoic. When Mizuki decides to leave the complex because her abusive boyfriend might come back looking for her and is saying goodbye to her neighbors, Kotaro attends while wearing a Tonosaman mask, refusing to answer when asked about it. It's obvious he's crying underneath, but absolutely refuses to acknowledge it.
- "Well Done, Son" Guy: Like many abused children, Kotaro believes that his parents abandoned him because he's not a good enough child. He still wishes to reunite with them again someday, and his daily training to become strong, polite manners, hygiene obsession, and stoicism are all his attempts to get them to come to like him should that happen. This is partially explained by Aota, who relates this to his own childhood and how he also blamed himself for his father's abuse back then.
- "Where Are They Now?" Epilogue: The ending for the last episode showcase the current lives of the various people that Kotaro met throughout his adventures.
- The older brother and his two siblings have been adopted and are more at peace.
- The phone scammer is shown playing baseball with his son.
- Aota is still doing his detective work but now he has his gifted spyglass and a photo of his Shizu Apartment friends on display.
- The dentist is still giving his regular check-ups.
- Kotaro's designer friend is still making clothes and is wearing the t-shirt design he made for the boy.
- Hide is still involved in the soccer club.
- The supermarket lady has given birth and is accompanied by her husband.
- Mizuki is seen living near a coastal city but is alot happier with her current life.
- Wise Beyond Their Years: Kotaro both acts and talks nothing like a real 4-year old, and in many ways appears much wiser than one might expect a kid his age to be. Justified in that he pretty much had to take care of himself even before going to live on his own due to his Abusive Parents.
- You Called Me "X"; It Must Be Serious: Kotaro usually calls Uda "the man that seduced my mother" out of his dislike for the latter and the way he was interested in Kotaro's mother Sayori during her marriage. However he'll occasionally refer to him as Uda-dono ("Lord Uda") when he speaks of him nicely, showing that he still recognises his good points and appreciates his efforts in making Sayori happy and reporting his father to the police when he saw Kotaro calling him for help.
