Tamaki introduces himself as the new kid. Tamaki Amajiki transferred to his new school during the spring. On his first day as a third grader, Tamaki could not give a proper self-introduction, and after the opening ceremony where they moved into the classrooms and formed groups, Tamaki was not able to insert himself into any group because he lacked the courage. Due to considering himself a boring person, Tamaki was not able to make any friends. In middle school during a Quirk Education class, Tamaki tried manifesting something but only managed to manifest a tiny plant on his hand due to his nervousness. Meanwhile, Mirio tried phasing through a wall but only managed to phase his hands through it. Some of Mirio's classmates laughed at Mirio's struggles, but Mirio was not disheartened at all and resolved to pull off his phasing properly next time. While walking home, Tamaki praised Mirio's optimism while lamenting his own lack of self-esteem. Mirio cheered up Tamaki and said that he will shine brightly like the sun and the reason he can give it his all is due to Tamaki being there for him. Although he was nervous, Mirio praised Tamaki's resolve to never give up which inspired him to do the same. Despite Tamaki's low opinion of himself, Mirio always thought of Tamaki as a talented person who is cool and super fun and sunny to be around with. After middle school, Tamaki and Mirio entered UA
Tamaki observes Class 1-A fight Mirio.
High School and they, along with Nejire Hado, eventually worked their way to the top, becoming The Big 3 of UA Tamaki chose his hero name to be Suneater, a name that was inspired after Mirio told him that he would outshine the sun. Tamaki, Mirio, and Nejire visit Class 1-A and explain about the hero internships. When Shota Aizawa asks them to introduce themselves, Tamaki is overcome with anxiety and struggles to imagine Class 1-A as potatoes. Eventually, he gives up trying and turns around. As Mirio challenges the whole class, Tamaki warns Mirio to hold back so he will not completely frustrate his enemies when they lose. When Class 1-A marvels at Mirio's Quirk, Tamaki thinks to himself how inexperienced they are for not recognizing all the hard work Mirio needed to refine and master his Quirk. Tamaki observes Class 1-A fight Mirio. Tamaki overhears Izuku Midoriya rallying his classmates to form a strategy to counter Mirio before they are taken down, despite their determination. Nejire points out to Tamaki that Mirio has gotten very strong, only for Tamaki to reply that he has been strong since he was a child but that he needs to learn to go easy on amateurs.
After the battle, Class 1-A is frustrated because they did not know how to fight Mirio's Quirk. Nejire wants to explain how his Quirk works but Tamaki tells her that it is Mirio's time to speak. Among all the 1-A students, Eijiro manages to catch his attention, so he decides to invite him to participate in the Work Studies with him at the Fat Gum Agency. Once there, the BMI Hero Fat Gum is surprised that Tamaki has brought someone, and remembers that Eijiro was one of the best participants in the Sports Festival. Fat Gum does not hesitate to compare him with Tamaki, whose nervousness always makes him be among the last. Tamaki is saddened by these statements. Fat Gum takes his interns out for patrol duty. In the Kansai Region of the Esuha Market, Tamaki and Eijiro Kirishima are patrolling the streets with Fat Gum. Fat Gum tells Tamaki that they need to fix his terrible mentality of his since he has a lot of talent, which stresses Tamaki. Tamaki thinks that the only reason Fat Gum scouted him was that he wanted to torment him, although Eijiro reassures Tamaki that Fat Gum was trying to encourage him.
Tamaki states that because he is not one of those optimistic Heroes like Mirio, to which Eijiro replies that he is not like that either, and there have been many desperate times where he could not do anything and he wants to close the gap so that he can stand amongst his fellow classmates. Tamaki knocks out a criminal. Suddenly, a fight breaks out with a thug attacking another group of thugs for doing business on his turf. The group of thugs manages to get away, only for them to land into Fat Gum. The thugs start submerging into Fat Gum's body. However, one of the thugs manages to escape from Fat Gum's body using their Quirk. The thug starts running away but is caught by Tamaki's octopus tentacles. Tamaki uses his octopus fingers to reel the thug in and slashes the thug through the face with his clam hand, which defeats the thug. Tamaki wonders if he did a good job, to which Eijiro replies that he was awesome. Fat Gum comments that Tamaki's Quirk has already been outclassing many Pro Heroes and the only aspect that he needs to focus on is his mentality, much to Tamaki's loathing. The crowd cheers for Fat and Suneater, but Tamaki gets easily embarrassed. In the crowd of civilians, there is a man who takes out a gun, wanting to help his brothers which are the group of thugs. Fat Gum takes notice of this and yells at the crowd to get down.
The man begins running away while Eijiro and Fat Gum chase after him.
The man fires the gun that releases a special bullet that hits Tamaki. The man fires another bullet, but Eijiro protects Tamaki and is hit instead. Fat Gum rushes to Eijiro and Tamaki's aid. However, Eijiro activated his Hardening before the bullet hit, which caused the bullet to simply bounce off him, much to the man's shock. Angry, Eijiro yells out that he will capture the man. Tamaki manages to stand up with no injuries from the bullet, which shocks the man who fired the bullet. Tamaki attempts to capture the criminal who fired the bullet but is unable to activate his Quirk. The man begins running away while Eijiro and Fat Gum chase after him. Fat Gum orders Tamaki to stay and guard the area while Tamaki replies that while he is not injured, he cannot activate his Quirk, which surprises Fat Gum. While Fat Gum and Eijiro deal with the gunman, the Police Force has rounded up the thugs thanks to Tamaki.
Tamaki asks one of them that the reason why he can't uses his Quirk is due to the bullet, but the criminal insults him and tells him to die, causing Tamaki to sulk. The policeman tells Tamaki that he can leave the rest to them. Tamaki has a bad feeling about the situation. Eijiro and Fat Gum manage to capture the gunman and turned him into the police. After this, a policeman comes running to tell Fat Gum that the criminal's gun is an unusual one. Tamaki is ashamed that he is unable to use his Quirk and hides his face using his hood, but thanks Eijiro for protecting him. Fat Gum decides to take his trainees to the hospital. He is very worried about Tamaki and wants him to be checked out, because he has never heard of drugs that can disable people's Quirks. Tamaki's Quirk slowly returns. Days later, Tamaki, Eijiro, and Fat Gum attend Sir Nighteye's hero meeting about the yakuza member Kai Chisaki, along with other heroes and some of the UA Student that also participates in the Work-Studies.
When Rock Lock interrupts to ask why kids are present considering that they will hold back the discussion when things get dark, Fat Gum defends his trainees and reveals they're directly involved in the case. He announces that Tamaki was shot with a bullet that harms Quirks. Mirio asks Tamaki if he is alright, to which Tamaki explains that he has recovered and can still use his Quirk, which he demonstrates by manifesting a cow hoof. Fat Gum follows up by explaining that Tamaki has been checked at the hospital after being shot and found out that Tamaki's Quirk Factor was damaged, but thankfully Tamaki was able to heal over time, meaning the bullets are likely still in a testing phase. Thanks to Eijiro's brave actions by protecting Tamaki, they were able to obtain a bullet with the contents still inside. Fat Gum disturbs everyone when he reveals that the Quirk Canceling bullets contained blood and cell samples from a human. Sir Nighteye adds that Izuku and Mirio encountered Overhaul's daughter, Eri, who had bandages running up and down her legs, and explains that Overhaul's Quirk gives him the ability to disassemble and reassemble objects. Sir Nighteye concludes that Overhaul is using his own daughter to produce those Quirk destroying bullets. Downcast, Izuku and Mirio explain what happened.
Mirio agrees with them.
Sir Nighteye concludes the meeting by informing that an operation will be carried out to dismantle the Shie Hassaikai and rescue Eri. With the meeting over, Izuku and Mirio explain to Ochaco, Eijiro, Tsuyu, Tamaki and Nejire what occurred between them and Overhaul. Both students are still crestfallen for being unable to save Eri. Tamaki is surprised to see his friend Mirio being so gloomy. Shota Aizawa arrives and encourages his students to keep fighting, truly believing they can save the girl next time. Tamaki and Nejire convince Mirio to snap out of his misery, with Nejire telling him that there is no point in feeling regretful. Mirio agrees with them. Tamaki joins the heroes in their mission to save Eri from the Yakuza. As the Heroes head down towards the basement but are surprised to see a wall before them. Mirio uses his Quirk to phase through the wall, with Tamaki explaining that Mirio's Hero Costume is made with special fibers from his hair, allowing his clothes to phase with him. Mirio has phased through the wall and sees that the path stretches on as Nighteye said. Mirio returns and tells the Heroes that the wall was thrown in the way to block them; Rock Lock suspects that it was Kai's Quirk that put the wall there in the first place. Izuku activates One For All: Full Cowl and Eijiro Kirishima activates his Hardening.
Mirio decides to go on ahead and phases through.
Using their enhanced might, Izuku and Eijiro shatter the wall together. Tamaki takes on Toya, Yu, and Soramitsu. Tamaki surprises that Kai is stalling them for time to hide everything and escape and starts becoming stressed out since their lives could be at stake. Mirio encourages Tamaki by saying that they will definitely rescue Eri. Mirio decides to go on ahead and phases through. Tamaki starts blaming himself for falling under pressure. Mimic causes the floor to open up beneath the Heroes, causing the heroes to fall down a single floor. The heroes are in a hall; three figures appear from the dust, revealing themselves to be three members of the Eight Bullets. As Fat Gum prepares for battle, Tamaki decides to battle the three Bullets himself in order to make up for falling under pressure. Suddenly, Tamaki, while manifested into a clam, appears before the group of Eight Bullets. He opens up the clamshell and grabs hold of the three villains with his octopus tentacles.
He tells them that he will be their opponents before throwing them onto the ground. Tamaki manages also to grab their guns and swords and crushes them by manifesting a crab claw. Tamaki sees that the yakuzas are buying time so that the ringleaders can escape with Eri and asks the Heroes and Police Force to go on ahead. Eijiro tries to stop him, but Tamaki is resolute in stopping the three villains on his own since Heroes like Shota are needed on ahead and tells Fat Gum that he will be fine. Before leaving, Shota disables the three Eight Bullets' Quirks. Tamaki pins the three down with his octopus tentacles and asks them to help Mirio since he tends to push himself too hard. Tamaki facing the Eight Bullets. Tamaki decides to put them to sleep and strikes them with his octopus tentacles. However, Tamaki injures himself after striking Toya's mask who reveals that he was hiding a knife in his mask.