Tamaki transferred to his new school during the spring, 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. Suddenly, Mirio Togata approached him after realizing that Tamaki was trying to say that he likes Heroes; it was this recognition that began the friendship between Tamaki and Mirio.
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 U.A. High School and they, along with Nejire Hado, eventually worked their way to the top, becoming The Big 3 of U.A. 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. In a few minutes, Mirio deafeat half of class 1-A.
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 remember that Kirishima was one of the best participants in the Sports Festival. Fatgum does not hesitate to compare him with Tamaki, whose nervousness always makes him be among the last. Tamaki is saddened by these statements.
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.
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 a 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 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 not able 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 thungs 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 in to the police.
After this, a policeman comes running to tell Fat Gum that the criminal's gun is an unnusual 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 being check out, because he has never heard of drugs that can disable people's Quirks.
Days later, Tamaki, Eijiro, and Fat Gum attend Sir Nighteye's hero meeting about the yakuza member Chisaki, along other heroes and some of the U.A. Student that also participatres in the Work-Studies. When Rock Lock interrupts to ask why kids are present considerind 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 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 Cancelling 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.
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 Chisaki. Both students are still crestfallen for being unable to save Eri. Tamaki is surprised to see his friend Mirio 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; Lock Down 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. Using their enhanced might, Izuku and Eijiro shatter the wall together.
Tamaki surmises 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 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. Shota's Erasure has ended, allowing Yu to activate his Crystallization and to grow crystals from his body which allows him to break free from Tamaki's octopus tentacles. Tamaki manifests his hand into a clam, but suddenly, it disappears because Toya used his Quirk to steal it from him. Toya remarks on their status as being the Eight Bullets; they had given up on life but their boss, Kai Chisaki, picked pieces of trash like them from the garbage heap and put them to use again. Yu is prideful in being just trash and is more than obliged to fulfill the expectations of Kai. Yu strikes Tamaki with his crystallized punch.
Tamaki manages to block Yu's crystallized punch by manifesting strong crab claw fingers and grabs hold of Yu's fist with a strong grip. Fueled by Mirio's confidence in him, Tamaki tells the three Eight Bullets to give up because he is Suneater, which is his Hero name that was inspired after Mirio told him that he would outshine the sun.
However, despite Yu, Toya, and Soramitsu being those worthless people, Kai Chisaki welcomed them with open arms into the Shie Hassaikai, stating that they should not be rotting away. This is why Toya does not care about being captured or any other consequences because Kai gave them worth and vows to kill anyone who gets in his way. Tamaki sees that Yu, Toya, and Soramitsu have been brainwashed into thinking that they have worth and asks the three Eight Bullets if they are fine with being used and thrown away.
Yu ignores Tamaki's question as a Hero like him could never understand and decides to finish Tamaki off by striking him with his crystallized arm. Tamaki manifests a chicken leg and uses its talons to flick a crystal shard at Toya, which distracts Toya and causes him to recoil in pain, preventing him from using his Larceny since he can only steal objects that he sees. Hojo strikes Tamaki with his crystallized arm. However, Yu is shocked that his crystallized strike has been mitigated. Suddenly, Yu's crystallized body has been clutched by Tamaki's large crystallized chicken leg. Tamaki is impressed with the trust the three Eight Bullets have in each other which has made them a good combination. As Soramitsu goes on the offensive while Toya is still recovering, Tamaki comments that while he may not understand their circumstances and anger, he does understand the hardened bonds they speak of.
Tamaki extends his large crystallized chicken leg, smashes the crystallized Yu into Toya and Soramitsu, and then smashes the three into the wall, further increasing the damage. Yu, Toya, and Soramitsu have been defeated. Tamaki states that the hardened bonds they spoke of the show that they are not just using each other for their own gain and comments that friendship is a powerful thing.
He removes their masks and ties up the three Bullets with one of his tentacles, which releases a small dosage of poison that paralyzes them. Tamaki begins walking away, but battered and tired as he is, he finally succumbs and falls unconscious.
After being unconscious for several minutes, Tamaki wakes up when he feels that something bad happened to Mirio immediately after the latter gets shot with one of Overhaul's Quirk-Erasing Bullets. Tamaki goes out in search of others, encountering a wounded and unconscious Mirio and several police officers who accompany him. While carrying Mirio, he saves Shota's life when he was about to be stabbed by Hari. Tamaki manifests his hand into a swordfish and pierces Hari's arm with the bill, causing him to drop the sword. The Police Force who demand that Hari surrender. Tsuyu Asui appears from behind and asks Tamaki to come with her to the surface.
Once there, Tamaki discovers that Izuku has managed to defeat Overhaul and rescue Eri. With this victory, the members of Shie Hassaikai are arrested, and the wounded sent to a hospital to recover from the wounds.
With the beginning of October, Tamaki goes to Sir Nighteye's funeral, who died because of the injuries he suffered in his fight against Overhaul. He is accompanied by the Work-Studies group, All Might, and Eraser Head. His Work-Studies with Fat Gum is put on hold.
Days later, Tamaki is one of the people who helps Nejire prepare for the beauty contest that will be held during the U.A. School Festival. During a visit of Mirio and Izuku accompanying Eri, Tamaki explains that Kendo from class 1-B will also participate, so Nejire is giving this all she's got. Just by thinking about the idea of performing in front of a huge crowd, Tamaki starts to feel bad due to nervousness.
The days pass until the festival finally begins and the beauty contest takes place. When is Nejire's turn, he wishes her good luck so she doesn't get nervous because of the crowd, although it is he who is really nervous for that reason. Like many people in the public, Tamaki is enchanted by his performance, comparing it as a fairy. Nejire ends up winning the contest, and Tamaki enjoys the rest of the festival with his friends.
Later on, Tamaki is present as Mirio and Shota inform Izuku and Class 1-A that Eri will be taken in by the school. After Mirio explained the growth of Eri's horn and the monitoring her, Tamaki pats Mirio on the shoulder and mentions if Eri's abilities become stable and she gains control, Mirio's Quirk could possibly return to him. Mirio laughs at his idea by stating it would be neat as he smiled at him.
With the Public Safety Commission's demand of all the students heroes participate in practical field training, Tamaki returns with Eijiro to the Fat Gum agency, and now Tetsutetsu joins them. Tamaki is nervous, with his face against the wall, commenting that "now there are two of them".
The Big 3 are taking care of Eri in her room when she suddenly starts crying, saying that her horn's started to feel unusual. While Mirio and Tamaki hurry off to look for Shota, Nejire stays with Eri, hugging and comforting her. Shota arrives and erases Eri's Quirk, gently patting her on the head and telling her not to worry.
The months go by until it's late March. Thanks to the police investigation and its spy Hawks, the Hero Public Safety Commission has found out the plans of the Paranormal Liberation Front and its allies. With this information the Commission organized a large force of Pro Heroes, divided in several teams to take down the villain organization.
One of the teams has the mission of storming the main headquarters of the Paranormal Liberation Front and arrest all its members. Tamaki is in the front linea along with Fat Gum. After the hero team led by Endeavor start to storm the Jaku General Hospital, the Villa Raid Team begins their assault on the Gunga Mountain Villa. 
The Paranormal Liberation Front is caught off guard by the surprise attack, which allows the heroes to take the initiative and defeat many of their soldiers. The heroes also sealed all the external secret entrances to a giant sanctuary beneath the mansion, leaving the interior ones only.
Tamaki and Fat Gum ask Tsukuyomi to joins them in sealing one of these entrances. Warriors of the liberation front guard the pathway with their lives but Tamaki performs his super Move Vast Hybrid - Chimera Centaur to take them down and nonchalantly gives a nice one-liner. Impressed by the delivery, Fat Gum says he wants to hear him say it again, only for Tamaki to be too embarrassed to do so.