A Sister's All You Need (妹さえいればいい。, Imōto Sae Ireba Ii.) is a Japanese light novel series written by Yomi Hirasaka (of Haganai fame) and illustrated by Kantoku. Shogakukan has published 13 novels since March 2015 under their Gagaga Bunko imprint. Two manga adaptations have been published by Shogakukan and Square Enix. An anime television series adaptation by SILVER LINK., with Hirasaka's involvement as the head writer, premiered on October 8, 2017.
The story follows the novelist Itsuki Hashima who is surrounded by various people, including a beautiful genius writer who loves him, a big-sisterly college classmate, a fellow male writer, a sadistic tax accountant, and his editor. As the story progresses, the underlying conflicts of dreams and goals surface, as each character attempts to achieve their dreams, in their own way. One such example is the rivalry between author Itsuki and his friend Haruto. Itsuki's stories are driven by a passion for stories about little sisters with praise from a selective yet strongly supportive fan-base, whereas Haruto's stories are given by victory and romance through more common, yet popular cliches. Each of their stories are riddled with common light novel themes and concepts, such as romantic comedy elements and erotic illustrations. They are all looked after by Itsuki's younger "brother" Chihiro, who in fact is his younger step sister.
A Sister's All You Need provides examples of:
- 12-Episode Anime
- Aborted Declaration of Love: Haruto has a crush on Miyako, however he found out her feelings for Itsuki and decided to "keep going on his pace."
- Babies Ever After: Itsuki and Nayuta end up having a son named Soma at the end.
- Brilliant, but Lazy/Bunny-Ears Lawyer: Everyone in the main and supporting cast outside of Miyako and Haruto. They all have some kind of eccentricity or slack off from their jobs, but they're all so talented at them that they can easily get away with it.
- But Not Too Foreign: Nayuta is part Russian.
- Covert Pervert: There's a fair amount of them. Namely Haruto and Ashley.
- Crossover: The anime has an extremely brief one with Animegataris, which ran in the same season and followed it in broadcast order. Itsuki, Nayuta, and Chihiro show up on the eyecatches of the latter series.
- Drowning My Sorrows: Kenjiro is often seen drunk when overly stressed with his job.
- Elegant Gothic Lolita: Ashley.
- Erotic Eating: Taken to super unsubtle nevels with Nayuta, who takes a boiled egg and deep throats it on chopsticks, in an attempt to arouse Itsuki.
- Fake-Out Opening: The first episode of the anime at first seems like an absurd sister-fetish fantasy story, until it's revealed to be the latest chapter of the protagonist's new light novel.
- Fetish: Setsuna has a butt fetish and Kaiko has an underwear fetish.
- House Pseudonym: Nayuta Kani isn't her real name. Even Itsuki doesn't know it. It's later revealed to be Kazuko Honden.
- I Want My Beloved to Be Happy: Miyako has feelings for Itsuki but instead chooses to back Nayuta.
- Little Sister Heroine: The concept is poked at a few times, but overall the trope gets its fair share of playing with:
- Itsuki's obsession with fictional little sisters is one of his driving forces. Some in-series productions, such as the imouto light novel seen in the first scene/episode one, display the trope with pride.
- In Chihiro's case, it's defied. Itsuki's father assumes that he's a significant threat to Chihiro because of his incredibly unhealthy obsession with younger sisters in fiction. As such, he forces Chihiro to present as male around Itsuki out of fear of what he'd do to her if he knew she's actually his sister. Furthermore, when he does eventually find out that his sister is a girl, he goes into a funk so wide he takes a hiatus from writing; since he refuses to see his sister like an imouto heroine, he recontextualized his obsession and found the whole practice gross.
- There is a younger sister that invokes the trope— Haruto's little sister is obsessed with him, but she is constantly rebuffed until she threatens him with her own suicide if he doesn't stay by her forever.
- Mangaka: Kaiko.
- Missing Mom: Itsuki's mom died 3 years before the start.
- Non-Indicative Title: The title of the series gives off the impression that an imouto romance is on the horizon, but little sisters overall have very little to do with the content. It's mostly a series about the publishing industry and creating light novels (with the occasional appearance from mangaka).
- Older Than They Look: Ashley's 32 but looks like a teenager.
- Once an Episode: Every light novel, in some way, shape or form, features the cast playing a tabletop game for a chapter.
- Ragtag Bunch of Misfits: Itsuki's friends. They consist of a beautiful genius writer who loves him, a big-sisterly college classmate, a fellow male writer, a sadistic tax accountant, and his editor.
- Sadist: Ashley makes her clients reveal their fetishes through their expenses, but raises their tax return in exchange.
- Secret-Keeper: Ashley is initially the only one among Itsuki's acquaintances who knows about Chihiro's real identity.
- Shameless Fanservice Girl: Nayuta cannot write unless she's naked.
- Sweet Polly Oliver: Chihiro hides her real gender at first because their father thought she was in danger when he found out about Itsuki's obsession during his novel debut.
- Take That!: The work in general can be seen as a criticism of Imouto in general, especially because the protagonist ends up losing all the pleasure he had about the genre, when he discovers that he has a real sister.
- The Trickster: Ashley.
- Wearing It All Wrong: The ribbon that Kaiko wears on her head? Yeah, that's a pair of panties. And she wears them on her face before she draws.
