"Only if you beat me in Kill Ballad..."

Kaito "Kai" Yashio (八汐 海翔) is a member of the Robotics Club and the main male protagonist of the series. He is an avid fan and skilled player of the mecha fighting game Kill-Ballad, which was based on the in-series anime, Gunvarrel. Although he is a member of the Robotics Club, Kaito is not interested in robots, and only joined to be by Akiho's side, by request of her sister Misaki.

Character Overview


Kaito is best described as lazy, relaxed, blunt and sarcastic- in short, the polar opposite of Akiho. He is easily the most rational of the two and never hesitates to tell Aki the impracticality of her goals. He rarely does anything that requires significant effort and is not shy about resorting to cheating to complete a task if it means he has to work less. Kai is also willing to give up something, in sharp contrast to Aki's unwavering determination, and has little or no faith that he and Aki can complete the GunBuild project before graduating.

Despite being a member of the Robotics Club, Kai has no real interest in robots, and is only really a member of the club by request from Misaki, who counted on him to look after Aki after she left. Ironically, he is a big fan of the robot fighting game Kill Ballad and can often be seen playing it, to the point that whenever he is told to do something he doesn't want to or asked for a favour, he tells them they'll have to beat him at it, which due to his skill, almost never happens. However, he nonetheless keeps his word that he'll do what they say if they beat him, which Aki eventually exploits by having him face off against Nae, who is one of the few people who can beat him at the game.

In keeping with his laid-back nature, Kai is generally very calm and level-headed, being able to keep his cool during the entire Robo-One tournament, as opposed to Aki, who freaked out whenever things weren't in their favour. However, he does have a breaking point; he dislikes it when people make fun of Elephant Mouse Syndrome and gets notably angry and annoyed when Kona says it sounds like an anime cliche, since the spasm attacks are extremely painful and he's had to put up with them for most of his life. He can also be quite manipulative at times, as shown when he blackmails Subaru into joining the Robotics Club by threatening to make his secret identity (Mr. Pleiades) public.

Behind his front of aloofness, Kai has been shown to be a kind-hearted individual who cares deeply for his friends, especially Aki, whom he has dedicated much of his time looking after since her sister left. Although he tends to disagree with Aki's decisions, he nonetheless goes out of his way to make her happy, a trait noted by Mizuka. Kai is generally the person Aki turns to when she has trouble making a decision, such as when he convinces her to accept help from JAXA after reminding her what her original goal was- not to finish construction on GunBuild-1, but to create a robot she could show at the Tokyo Expo. He's also the one to get her back on her feet when she contemplates giving up on her dream, though Aki claims that in doing so, he sounds like a completely different person.

Mizuka's sudden demise shakes up Kai badly, to the point that he ends up having nightmares about her, in which she blames him for not doing more to prevent her death. However, he still covers up his trauma with sarcasm, something Aki quickly catches on to and calls him out for. Aki claims that he's always been like this, saying that whenever he feels down, he always hides it behind some joke or sarcastic comment. In general, Kai tends to be a very reserved person, which is perhaps best shown when he catches Aki off-guard with his love confession, and he suspects that he did too good a job at keeping his feelings to himself.

Skills & Abilities

Similar to Akiho, Kaito chronically suffers from Elephant Mouse Syndrome, which he obtained from the mysterious SS Anemone incident. However, Kai's Elephant Mouse Syndrome causes him to experience a time distortion of perceiving seven seconds to every one second, as opposed to Akiho, who sees five minutes over a few seconds. As a result, when Kai is under extreme mental or physical stress, he experiences something that he refers to as "Slow-Mo," which he can take advantage of to obtain a kind of temporary super-human reflexes.

After sinking much of his free time into Kill-Ballad, Kai is an expert at the game. This mastery of Kill-Ballad carries over to his robot operating abilities due to the Robotics Club modeling the robot controls after the Kill-Ballad control pad.


Kaito seems to have an affinity for red accents. He is typically seen in his school uniform and wears a red shirt underneath along with a red wrist watch. His eyes are a crimson-brown and his hair is a distinctive red. Kai's pokecom, which has a red Kill Ballad sticker applied to it, is fastened on his waist.


Kaito was a childhood friend of Akiho and her older sibling, Misaki, would serve as a sisterly figure to him as well. He was subjected to the mysterious SS Anemone Incident that left him and hundreds of others, including Akiho, in a comatose state for a brief time. After recovering, Kai learned that he and Aki had developed a bizarre chronic disorder dubbed Elephant Mouse Syndrome. Soon after, Misaki would graduate, but before she left, she requested Kai look after Akiho.


Love Interest

  • Akiho Senomiya: Akiho is a childhood friend of Kaito and the two share a very close bond. Akiho refers to Kaito by his nickname, "Kai" and he in turn calls Akiho, "Aki." Though Aki's brash enthusiasm starkly contrasts with Kai's lazy indifference, Kai is a loyal ally and ever-present supporter to Aki. However, Kai never openly shows his support, instead preferring to do work behind the scenes. Though Kai cares deeply for Aki, the two do tend to bicker from time to time. Kai later confesses to being in love with Aki, and the two share a kiss.


  • Subaru Hidaka: Kaito and Subaru share an awkward relationship. Though there is a mutual respect between them, Subaru is frequently annoyed by Kaito's blunt personality and general laziness. Despite this, Subaru and Kaito often find common ground with their shared realistic views and are typically shown to get along more often than not.
  • Junna Daitoku: While Junna is initially hesitant of the Robotics Club due to a fear of robots, Kaito's kindness eventually coaxes her into joining. The two are quite close and Kaito often serves as a supportive crutch for her in overcoming her insecurities.
  • Kona Furugoori: Though he is at first alienated by her social awkwardness, Kaito and Kona quickly become close friends. Kaito is always wary of Kona's tendency to neglect eating and dedicates a generous amount of his time looking after her. Bonding over their mutual love of Kill Ballad, Kaito at one point collaborates with Kona to stomp out players who cheat at the game.
  • Misaki Senomiya: Growing up, Kaito was under the tutelage of Misaki and looked up to her as a kind of sibling role model. After Misaki adopts an aloof disposition and distances herself from Akiho, Kaito tries to shine logical explanations on why Misaki is acting in such a way, but never loses faith in the role model she once served as to him.
  • Mizuka Irei: After Misaki graduated and left Tanegashima, Mizuka acted as a surrogated sister to Kaito, dutifully looking out for him and Akiho. Kaito often comes to Mizuka for advice or assistance, but always at the cost of eating one of Mizuka's special nikuman.
  • Nae Tennouji: Kaito and Nae quickly become close friends, often playfully teasing one another. Nae is one of the few people to beat Kaito at Kill-Ballad.


  • Kaito's player name in Kill-Ballad is "Umisho" and is ranked 5th in the world. Later he is ranked 2nd because it revealed the best three are dead.
  • Kaito tends to eat a "Space Candy" when he is ready to get serious about something.
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