The Battler Party Arc is the 5th Story Arc of the Welcome to Demon School! Iruma-kun manga series.
The arc centers around the senior students recruiting the first-years into their Battler divisions (the demon world's version of school clubs), which they go on to compete in the Battler Party festival for rewards. Iruma joins Kirio's Magic Tools Research division in order to take part in the festival, but it soon turns out that Kirio is an evil demon in league with the villainous Thunder Lord Baal, who's got a sinister plan going on behind the scenes. To kill many people by blowing up Babyls Demon School. Thus, it becomes a mission for Iruma to put a stop to Kirio's plan. In the end, Iruma manages to put a stop to Kirio, which results in the latter's arrest. Iruma is also rewarded with an increase to Rank 3 (Gimmel) by winning the Battler Party's Tricky Prize where despite breaking many rules, he won the overwhelming support of the students who enjoyed watching his division's fireworks show.
The arc consists of chapters 18 to 37, and was adapted into episodes 11 to 20 of the 1st season of the anime.
Battler Party Arc Summary
Chapter 18: The Battler Challenge
The yearly Battler Party event is just around the corner at Babyls Demon School. Battler divisions, which are basically the demon world's version of school clubs, will get to show off what they're capable of in a school festival to make a name for themselves. The clubs who get the top scores during the festival receive rewards, such as demon rank promotions, which gets Iruma interested due to his goal to rise up in the rankings, and just sounding fun overall. Iruma remains in the cafeteria of the 1st-year tower alongside Azz and Clara as many upper class demons come charging in to begin the rookie hunt.Chapter 19: Rookie Hunt
Iruma gets caught up in the demon rookie hunt where upperclassmen go around school hunting freshmen students to join their Battler division. He receives many Battler division offers, including Ameri trying to recruit him for the Student Council. Before Iruma could make a decision however, his Ring of Gluttony forcibly pulls him along until eventually crashing into a glasses wearing demon, Kirio Ami.Chapter 20: The Demon Without Magical Engergy
Upon meeting the senior student, Kirio, Iruma sees that he's a demon with weak constitution. In addition, he's looked down on by the other students for being a low-ranked upperclassman, and is someone who needs to keep magic stored in a neck pendant to allow himself to use magic. Before moving on, hearing Kirio's desire to make magic tools that will allow for weak demons to keep up with the strong leaves an impression on Iruma.Touring around to different Battler divisions, it's shown during Iruma's practice with the Dodgeball division that Sullivan had set up Iruma's ring to allow him to use magic. The ring is now set with 3 different power levels, as well as a trump card mode above the 3 that Sullivan warns should only be used for emergency as it will release all energy from the ring. Iruma's school tour eventually leads him to the Magic Tools Research division where he sees Kirio as its only member.
Chapter 21: Magical Tools Research Division
Iruma enters the Magical Tools Research to help Kirio after an explosion occurred trying to do an experiment. Along with explaining many other magic tools to Iruma, Kirio shows off his main project; a machine he calls "Gabu-ko" that's capable of enhancing the power of a magic tool. Kirio once again states his goal to help weak demons get the same treatment as the strong, which Iruma can relate to due to his lack of magical energy. As a result, he decides that the Battler division he will be joining is Kirio's. Much to Kirio's surprise, Azz and Clara also end up joining his division since the two already decided to go wherever Iruma goes. Iruma also calls up Ameri to provide her the bad news that he's not joining the Student Council.Chapter 22: At One With Familiars
At the start of a new school day, a rookie teacher named Bars Robin tries to make an impression on his first day of work. Bars holds a class with the freshmen to teach students how to communicate better with their familiars. Thus, resulting in Iruma needing to summon Kalego again, much to the latter's irritation. However, Kalego forces himself to go along with it due to it being the teacher's goal to help their students. Kalego eventually takes over the class from Bars once it became clear that Iruma's the only one who knows how to properly take care of their familiar.Chapter 23: Thirteen Dinner
At a noteworthy place within the demon world called Babel Tower, the leaders of the demon world hold their regularly scheduled Thirteen Dinner meeting that's used to discuss, and resolve, the current issues going on. One of the demons at the meeting, Thunder Lord Baal, is shown to not get along well with the others, but apart from him, they all agree that the problems would be resolved quicker if they finally picked a true Demon Lord ruler amongst the 3 prime candidates: Lord Sullivan, Lord Beliard, and Lord Levy. Unfortunately, the debate remains at a standstill as said 3 have no interest in taking the position, and would rather compare who has the best grandchild. Sullivan is then caught by surprise when Chief of Demon Security, Azazel Henri, arrives to take the former into custody under suspicion of illegal visits to the human world.Chapter 24: The Battler Debut
Sullivan calls home to inform Opera of the situation, which Opera assures Iruma that there's no problems. Back at school, the Magic Tools Research division begin their preparations for the Battler Party. However, Iruma sees that they got an issue regarding their division being given a really small courtyard venue location for their festival stall due to no one taking Kirio or his division seriously. Combining the ideas of his teammates, Iruma decides on fireworks to be the project that their division shows off for the festival. He explains that they would be utilizing the endless sky to stand out rather than trying to show off from the tiny stall they were given. Kirio agrees with the idea, and suggests that they spend the night at school to work on the fireworks project.Chapter 25: The Ones Who Prepare
Iruma, Azz, Clara and Kirio basically have a sleepover within the Magic Tools Research room in order to work on the fireworks project. However, the attempt at making a firework ends up exploding on them. Here, Kirio shows off his Barrier bloodline ability to the group, which explains how he's able to keep himself from getting seriously injured whenever his experiments explode on him. Overall, Kirio notes their main issue that since no one really knows what fireworks actually are, they got no reference to start their work from. This gives Iruma an idea to ask Ameri for a favor to borrow the volume of "First Love Memories" that has an image of a fireworks show. Despite initially refusing, Ameri pretends to leave the book for Iruma upon hearing that he's planning to make fireworks; something she's very interested in seeing.Thanks to getting an image of the fireworks to start working from, Iruma and company eventually succeed in making a test firework. Kirio then takes a private call where it turns out that he's a subordinate of Baal, who Kirio refers to as his "big brother" to keep people from knowing who he's talking to. Baal is revealed to be an evil demon having been the one that tipped off the police about Sullivan. The Thunder Lord orders Kirio to destroy the school using "that" device while Sullivan is away, which Kirio happily agrees to. Thus, revealing that Kirio is evil as well.
Chapter 26: Kirio's Hidden Room
The teachers, Dali Dandalion and Suzy, make an announcement speech to the school explaining how the Battler Party will be an opportunity for the 1st-years to show off, and that their parents will be attending. In addition, they reveal the rewards for the 3 Battler divisions who achieve top score. 3rd place gets the Effort Prize; a gorgeous Battler room. 2nd place gets the Impressive Prize; increased Battler division funding and a mention in an article. Finally, 1st place will get the Special Prize; two rank-ups for the division leader, and one rank-up for the other winning division members.As the festival is being set up in the campus courtyard, Iruma notices that Kirio is strangely absent from helping get their division's fireworks venue set up. Kirio meanwhile is on his own within the school entering a hidden room only he knows about. He had already set up the Gabu-ko machine within the room, and plans to use it to blow up the school during the transition phase between the starting Festival Eve and the Main Festival. The order from Baal being to make as many casualties as possible. However, Kirio is suddenly caught off-guard by the sudden arrival of Iruma entering his hidden room.
Chapter 27: Two Feathers of the Same Bird
Shortly beforehand, Iruma had been searching around for Kirio, but was once again forcibly dragged along by the Ring of Gluttony to the entrance of Kirio's hidden room. Despite being surprised by Iruma's sudden appearance, Kirio goes along with it by explaining that the hidden room was originally a secret location for the Magic Tools Research division to do their work. He also shows off a large one-way soundproof window looking down at the campus courtyard where the Battler Party festival will be taking place.Hearing Kirio talk about how everyone looks the same from high-up, Iruma is once again reminded of the former's goal, and states that their division should aim for the Battler Party's special prize. In return, Kirio finds Iruma's determination incredible and believes the two of them to be a good match. As they leave the hidden room, Kirio asks for Iruma to keep the place a secret, which Iruma agrees to. The next day, the starting Festival Eve for the Battler Party begins.
Chapter 28: Beginning of the Festival Eve
At their homes, Iruma, Azz, Clara, and Sabro are all seen preparing themselves before heading off to school. The Battler Party then begins Festival Eve, which is basically the students having fun and showing off their Battler divisions before doing things for real in the Main Festival. Iruma, Azz and Clara have finished setting up their venue's rocket launcher, which Clara accidentally lights the fuse. However, they're surprised to see nothing shoot out as it turns out that the large firework ball had gone missing. Sure enough, Kirio is seen having taken the firework ball to his hidden room since his plan to destroy the school requires it.Chapter 29: Ambition Stored Away
Sullivan remains in custody by the police, but is seen having fun with the guards, which Henri finds hard to believe that the seemingly gentle Lord is guilty of doing anything wrong. Baal is shown to be with Henri assuring the Security Chief that his information is legit, and gives a warning that this might just be the calm of the storm. Sullivan meanwhile feels something is amiss and begins to worry about his grandson.Iruma, Azz, and Clara enter the school to search for Kirio. The latter remains within the hidden room thinking about how Baal views Kirio's twisted persona as not a mistake. That Kirio is the very essence of what a demon should be. Kirio then breaks his neck pendant revealing that it's not a magic storing device, but an item that was restraining his true magic power to act as a weak demon. With his magic released, Kirio covers the entirety of Babyls Demon School within a large Barrier box. The box also results in many Barrier walls going up within the school, such as one splitting up Iruma from Azz and Clara within a school hallway.
Chapter 30: Kirio's Maze
Students all around the school become confused by Barrier walls blocking their way at seemingly random locations. Kalego tests the strength of the walls, and concludes that the magic is so powerful that only a demon at the level of Rank 10 (Yod) will be able to destroy the Barrier box. To keep the students from panicking, Kalego and a fellow teacher, Dali, use the Broadcast division to announce the sudden Barrier box as a maze game to lead all the students to the courtyard for safety. Meanwhile, Kalego makes his way to the management warehouse to check the student files for people with the Barrier ability. He comes across Kirio's file, but remains worried that having all the students brought to the courtyard might be Kirio's plan to begin with.Within the hidden room, Kirio has set up a smaller Barrier replica of his large box in order to keep an eye on the locations of the students, and allows him to change up the Barriers of the large box to lead them all in the direction he desires. He's also placed the fireworks ball atop his Gabu-ko machine, which is enhancing the ball's magic power to have it make a large explosion. Overall, Kirio's plan is to lead all the students to the courtyard, and then kill them with a large explosion using Iruma's fireworks. While he works, Kirio's attention is suddenly brought to a magic dot making its way through the Barrier maze replica towards the hidden room's location. He easily assumes that it's Iruma given that the boy is the only one who knows about the hidden room.
Chapter 31: Clara Squad Captain and Azu Commander
The story jumps back a bit to show Iruma's plan. With Azz and Clara's help, Iruma's able to quickly make his way through the school's Barrier maze using a man-made map of the school, and the Magic Tools Research division's paper magic dolls to scout out the Barrier walls beforehand so that Iruma would know where to go. Meanwhile, Ameri and the Student Council take over in the courtyard to help the teachers keep the students from panicking. Eventually, Iruma makes it back to the entrance of Kirio's hidden room.Chapter 32: Desires From the Heart
Despite the entrance being blocked by another Barrier wall, Kirio allows Iruma to enter. Iruma questions Kirio if he really did set up the Barriers and took the fireworks, which Kirio easily admits to it, and that he plans to blow up the school. Kirio tells Iruma his backstory of how he started off as such a weak child that he just ended up disappointing everyone around him; including his own Ami family to the point that they sent him off to the Demon Children's Garden correctional institution.There was one young demon girl student that he got along with there to the point of her showing him her lucky charm. However, she ended up falling into crying despair after Kirio fails to save the charm with his weak Barrier ability from falling into a dark abyss. In the end, Kirio didn't feel bad about it, but instead felt thrilling ecstasy at the sight of seeing someone in despair. In the present, the sight of an ecstatic and evil Kirio reminds Iruma of how he's a human living within the demon world.
Chapter 33: Desperate Expression
Continuing his story, Kirio explains that upon arriving at Babyls Demon School, he sought out the Magic Tools Research division after hearing that there are people there similar to him. The members are put off by Kirio's twisted persona to the point of the division leader, Baal, appearing to find out what's going on. Kirio questions if he's a broken demon due to his out-of-the-ordinary twisted persona, but Baal assures him that nothings weird. That Kirio is just experiencing Ancestral Return where he's inherited the blood of how demons originally acted in the past. Baal reveals that he, and his division members, have gone through something similar, and that they long for the days where demons were all about chaos. Kirio is left impressed by Baal's ambition, and officially becomes Baal's subordinate. In return, Baal treats Kirio as a younger brother, and goes about teaching the demon everything he knows.Back in the present, Kirio reveals to Iruma that since Babyls Demon School is the symbol of the demon ranking system that keeps everything in order, the plan is to blow up said symbol to make the rankings, and the overall demon world, fall into chaos. He taunts Iruma that the boy's fireworks invention has allowed this plan to come to fruition, and becomes estatic at the thought of seeing Iruma fall into despair once the boy realizes that he's about to lose all that he cares about. However, the sight of Iruma remaining calm leaves Kirio stunned in disbelief. As it turns out, Iruma is someone who can't fall into despair as he's already lived through enough painful experiences in the past to know that nothing good comes from falling into despair. Thus, making Iruma the exact antithesis and greatest enemy of Kirio. Iruma then grabs the fireworks ball off of Gabu-ko, and claims that he will destroy Kirio's ambition with his own ambition by saving everyone.
Chapter 34: The Outbreak of Magic Power
Kirio finds Iruma's claim impossible to believe since the fireworks ball is set to explode even after being removed from Gabu-ko. However, Iruma surprises him by running for the window, and jumps out. As the countdown begins to start the Battler Party's Main Festival, Iruma activates his Gluttony Ring's 2nd highest Ifrit Mode to create a serpent dragon made of magic that carries the fireworks ball within its mouth towards the sky. Much to Kirio's excitement, the dragon serpent's movement is stopped due to the strength of Kirio's large Barrier box that's surrounding the school. However, Iruma shocks him again by activating the ring's strongest emergency Pandora Mode; turning the serpent dragon into an even more powerful form that shatters the Barrier box, and continues on towards the sky. Once the countdown reaches 0, a large fireworks explosion occurs high above the school much to the excitement of all the watching demon students as they get to see a firework exploding for the first time.Meanwhile, Kirio is shown to have jumped after Iruma since the boy went unconscious using all his magic power to activate Pandora Mode. Kirio had summoned up a Barrier to save the boy from falling to his death, but the demon is left in despair knowing that Iruma just destroyed everything he had worked on for years, and calls Iruma idiotic for falling unconscious while not caring about possibly dying from the fall. In the end, Kirio admits his loss since Iruma proved that his ambition to save everyone was greater, but he comes to view Iruma as a guy with wicked intention.
Chapter 35: Never Give Up on Anything
While unconscious, Iruma hears Kirio warning him that the demons he should watch out for the most are those like him who've "returned to the originator." Iruma then wakes up back in the hidden room, but is being looked after by Sullivan, who's finally returned to the school. Sullivan explains that it was thanks to teacher Bars using his Bullseye Shot bloodline magic that's capable of going through any obstacle to reach its target, even through Kirio's powerful Barrier box. Bars had fired an arrow with a note attached to it to Sullivan's location to inform the chairman of what happened. As a result, Sullivan left police custody on his own terms to quickly return to Babyls, and saved the school from the sparks of the large fireworks explosion that was going to drop upon the students using his powerful object stopping magic.Iruma remains confused about what happened to Kirio, which Sullivan explains the situation that Kirio was taken into police custody, but refused to admit that anyone worked with him. Sullivan also tells Iruma that Kirio left him with the message and that he hopes to enjoy activities with Iruma again somewhere down the line. The chairman then picks up Iruma onto his shoulders, and shows him off to all the demons celebrating at Iruma for showing them the fireworks; including Ameri. Though she confuses Iruma when she claims that they were supposed to view it together. Using a loudspeaker, Iruma reveals to everyone that the fireworks were done by the members of the Magic Tools Research division. Along with naming himself, Azz and Clara, Iruma makes sure to announce that Kirio also played a part since he enjoyed the time he spent with Kirio despite him proving to be a fearful demon.
Chapter 36: Spending Time With Family
The next day, the Battler Party's Main Festival officially begins. Students go about showing off their Battler divisions in front of the parents, as well as to those who are evaluating their performances. Iruma and Azz are seen working their fireworks venue, which they're introduced to Clara's large family. Iruma is also introduced to Azz's overly loving mother, Amaryllis Asmodeus, who's one of the 13 Crowns that lead the demon world. With time to spare, Iruma gets to have fun enjoying the festival with Sullivan and Opera. He meets Sabro's younger sister, Silvia, helping out her brother's division, and watches as Opera wins many festival stall rewards. In the end, Iruma comes to view Sullivan and Opera as his wonderful family. Eventually, the announcement by the Broadcast division is made that all votes are in regarding who won the Battler Party.Chapter 37: Glorious Commendation
The students arrive in the school auditorium to begin the final event of the Battler Party; the Awards Ceremony, which Ameri serves as the spokesperson to announce the winners. The Succubus division won 3rd place for their ability to make the festival as lively as can be. 2nd place went to the Magecraft Development division for showing that any student will have the ability to create their own magecraft. And finally, 1st place went to the Broadcast division for proving their ability to calmly respond to unexpected situations, which resulted in them having to work relentlessly throughout the festival. Some are left disappointed that the Magic Tools Research Division wasn't acknowledged, but it was already decided that they wouldn't be getting votes due to what division leader, Kirio, tried to pull.Kalego then takes the stage to announce a new reward known as the Tricky Prize. He explains that there was one specific team that broke many school rules, but in the end was able to win the overwhelming support of the students, which is reason enough for them to be rewarded rather than punished. The prize is increasing the rank of a division's representative by one, which Azz and Clara happily push Iruma forward. The result is Kalego promoting Iruma's badge up a rank to Rank 3 (Gimmel), but he also scolds Iruma for not relying on the teachers more to help resolve the Kirio incident. Everyone celebrates for Iruma only for the boy to realize that his original plan to not stand out has taken another major hit. Meanwhile, Iruma is seen having become noticed by Ameri's dad, Henri.
