When he is teamed with Rikido Sato as "Team F" after being randomly drawn.
Shota announces to Class 1-A that their lesson in Foundational Skill of Heroics will be the Trial of Rescue, and will take place at the Unforeseen Simulation Joint (USJ) Facility, a practical training area that is designed to simulate any kind of accident or disaster. One of the teachers for the lesson, Space Hero Thirteen.
However, before the lesson begins, a black portal opening up and dozens of villains come through it. Shota orders Thirteen to evacuate Class 1-A and try alerting the rest of the school while he runs to deal with the villains, however Kurogiri appears and uses his quirk his Quirk to teleport most of the Class 1-A students to different areas of the USJ. Koji is teleported along with Fumikage to the Downpour Zone, where a group of Villains were waiting to ambush them.
Due to the situation, Fumikage explains to Koji the weaknesses of his quirk. And since that moment the two face the villains until Present Mic comes to their aid, defeating all of them. After the League of Villains is defeated, Koji is seen with his class, having survived the Downpour Zone with little trouble.
Koji places 20th in the Obstacle Race, allowing him to participate in the next event, the Human Cavalry Game. He then teams up with Toru, Kyoka, and Rikido. Koji fails to advance to the tournament event due to his team being unable to accumulate enough points to advance.
Two days after the Sports Festival, Koji is in class. During the Hero Informatics period where the class has to decide on potential Hero names, Koji writes down and shows his Hero name: "Petting Hero Anima".
After Class 1-A is finished formulating their Hero names, Koji is given a list of 40 work places in order to choose a work place that he wants to train at. On the day of the work place training, Koji is at the train station with his class so that he can travel to the work place of his choice by train.
Present Mic uses his Voice Quirk to keep Kyoka and Koji off guard. Annoyed by Present Mic's loud voice, Kyoka tells Koji to command the nearby animals to attack, but Koji is unable to due to Present Mic's voice being too loud, in addition to it likely having already scared off the wildlife.
Kyoka and Koji manage to get a little closer to the escape gate, but Kyoka notes that Present Mic will be at the escape gate and that no matter what option of victory they choose, a standoff is inevitable. Present Mic uses his loud voice again; Kyoka notes that they cannot get any closer as long as Present Mic is using his Quirk. Kyoka sees an ant and comes up with an idea; she asks Koji if he can control bugs, but his terrified reaction indicates that he doesn't like bugs. Present Mic uses his loud voice once again; Kyoka tries to counteract with her Earphone Jack but the sound of her heartbeat doesn't do anything against Present Mic.
Present Mic continues using his loud voice against Kyoka and Koji who are unable to handle it. Out of options, Kyoka asks Koji if he can control insects to which he approves. Kyoka uses her Earphone Jacks to break a rock, which reveals dozens of insects, much to Koji's terror. Kyoka tells Koji that she understands his phobia but using the insects to attack Present Mic is the only plan she can think of because their opponent is too strong. Kyoka encourages Koji to follow through with her plan.
After seeing Kyoka's bleeding ears, Koji is ashamed that he is running away from this fight and realizes that he can only continue being at U.A. by overcoming his fear. Koji musters up his courage and though trembling with fear, he uses his Anima Quirk and commands the insects to attack Present Mic while Kyoka is annoyed, he picked that moment to talk. At the escape gate, Present Mic sees that time is nearly up. Suddenly, dozens of crawling insects break out from the ground near his left leg, and he realizes that the insects traveled to him by moving underground; a place where sound is ineffective. Present Mic is paralyzed in fear when the insects swarm onto his leg and cause him to faint in horror, allowing Koji to run through the escape gate while carrying an injured Kyoka in his arms.
Back in class at U.A., Koji learns that he passed the written test and will go with his classmates to the forest lodge which is a boot camp. Koji along with his class go to Kiyashi Ward Shopping Mall to buy necessities for the forest lodge.
The next day, after an a meeting between Deku and Tomura Shigaraki at the shopping trip, Shota informs Class 1-A that the destination for their lodge trip has been changed and the new destination will only be announced on the day of the event. The first semester has come to a close and summer break has begun. On the day of the event, Class 1-A boards a bus that will take them to the forest lodge destination.
An hour later, Class 1-A’s bus stops for a restroom break. There, they meet Pixie-Bob and Mandalay, two members of the Wild, Wild Pussycats, who challenge the students to reach base camp past the forest in three hours. Then, all Class 1-A is forcibly thrown into Beast's Forest by Pixie-Bob's Quirk. Mineta goes into the forest to find a place to piss, when suddenly, he is confronted by a beast. Koji tries using his Quirk to control the beast but it does not work due to the beast being made out of dirt. Izuku, Shoto, Tenya and Katsuki mobilize and use their Quirks to destroy the clay beast.
The forest soon fills with more clay monsters, and students use their quirk to destroy them. Koji commands birds to distract the beasts so that they can be destroyed by his classmates. After several hours, Class 1-A manage to cross the forest and arrives at the base camp exhausted and battered, where they can finally rest and eat.
The next day at 5:30 AM, Class 1-A are outside the training camp cabin. Shota greets his students and tells them that they will undergo reinforcement training to strengthen and upgrade their Quirks. In order to increase the reach of his Anivoice, Koji is doing vocal exercises to build up his vocal cords. It’s also good for helping him become less shy.
After another day of intense training, Koji prepares to participate in a courage test organized by the Pussycats. The Vanguard Action Squad of the League of Villains invaded the place that night, attacking the students and tutors,, leaving the place after kidnapping Bakugo. Two days later, Koji, along his classmates, visits those who ended up hospitalized due to the attack. Once there, he knows the plan of Eijiro and Shoto to rescue Katsuki. Although he does not participate in it, he does not oppose the intentions of her classmates.
Following the intense villain attacks toward U.A. students, Nezu transformed U.A. into a boarding school in order to protect the students. When Class 1-A arrives at their dorm, Shota scold them for disobeying the rules and allowing five students to rescue Bakugo. He further more says he would have expelled everyone but Bakugo, Hagakure and Jiro (due to them being captured and hospitalized, respectively) from the school, if it weren't for All Might's sudden retirement and asked them to stick to the rules from now on.
Afterwards, the class moved in and decorated their room, then Mina suggests that they make a room showcasting competition. As they enter Koda's room, Mina and Ochaco start to fawn over his pet bunny and play with it. The next day, Shota announces that Class 1-A will be working on developing their own special moves, much to the class' excitement. The class visits the Gym Gamma, where Cementoss creates a training ground for the class with Ectoplasm using his quirk to create villains for the class to practice their moves on. In preparation for the Provisional Hero License Exam, Koji decides to upgrade his hero costume, adding new elements, such as a mask that covers his entire face, with holes above over his mouth so his voice still can be heard when he's using his Quirk.
When Yuga is about sacrifice himself to save Tenya, the beam that Yuga shot up in the sky gave him the perfect opportunity to send birds down to the other students that were after Yuga and Tenya. He along with the rest of Class 1-A pass the first test. He and the rest of Class 1-A pass the second task and get their Provisional Hero License except for Shoto and Katsuki.
The next day, after the opening ceremony, at classes, Shota talks about Hero Work-Studies and days later, introduces to them the The Big 3, the best U.A. students: Mirio Togata, Tamaki Amajiki and Nejire Hado. They will be the one who will introduce them to the Hero Work-Studies.
Koji, like his classmates, is confused by the eccentric personality of the Big 3, and is also surprised when Mirio challenges them all to a fight. At Gym Gamma, the entire Class 1-A attacks him, but Mirio manages to defeat the entire Class 1-A alone without breaking a sweat thanks to his Quirk Permeation.After the fight, while Class 1-A recovers from their defeat,Mirio advises them to participate in the course, since it will help them improve their abilities and career as heroes, just as it happened to him.
Weeks later, after the police raid at the base of Shie Hassaikai, Izuku, Eijiro, Ochaco and Tsuyu return to their dormitories at the school, where Koji, along the entirety of Class 1-A, is checking to make sure they are doing okay after their mission. Koji even brings his pet rabbit to help them cheer up.
Shota Aizawa announces that U.A. High School will be having a School Festival, which is sponsored by the other U.A. departments. He tells Class 1-A to pick out a program to perform at the festival. Tenya Iida asks for ideas to class 1-A, but each one has his own and they don't reach an agreement.
At Heights Alliance, Class 1-A along with Koji finally decide to accept Mina's idea of carrying out a dance performance for the U.A. School Festival. Then Minoru reminds them all that dancing requires music, so the whole class looks at Kyoka. She believes that his music is nothing special and not very heroic-like, but Koji, along with Denki, encourages her to lead the band and play in the festival, saying that music can help put smiles on people's faces.
Class A-1 students are divided into three groups, Band team, Dance team and Staging team, Koji is part of the staging team with Shoto, Eijiro and Sero. During the following weeks, the various teams practice their respective functions. On the appointed day, the Class 1-A performance ends up being a huge success.
Koji participates in the first round of the Joint Training Battle. He is part of the Class 1-A team, formed by Tsuyu Asui, Eijiro Kirishima and Denki Kaminari against Class 1-B team, formed Ibara Shiozaki, Kosei Tsuburaba, Hiryu Rin, and Jurota Shishida. Hitoshi Shinso from Class 1-C is added to Class 1-A's team.
When the match starts, Koda uses his Quirk to send pigeons to explore and find the B team members. The pigeons return to inform him that Ibara is alone, probing over wide range with her Vines Quirk. Class A heads towards her position, but they are ambushed by Jurota, who smashes both Eijiro and Tsuyu through nearby pipes. He reveals that his team knew Koda would find them with his Quirk and used Ibara as bait. Kosei Tsuburaba follows up by trapping Koji inside an Air Prison.
A confrontation between both team takes place, and Tsuyu captures Kosei with her tongue, and takes him back to the jail to eliminate him from the match, being persecuted by Jurota. Koji and Eijiro block his path. Koji tries to use a small swarm of insects to stop Jurota while Eijiro attack him with his Red Gauntlet, but both fail, and Jurota tosses Eijiro into the air, allowing Ibara to capture him with her Vines. Jurota retreats, carrying Koji while muffling his ability to speak, and the two Class 1-A students are put in their jail, eliminating them from the match.
Despite this setback, Class 1-A wins the set 4-2. When Shota Aizawa asks his students what they learned from the battle, Koji responds that he needs to be able to give better instructions to insects, so Shota tells him to keep thinking about his weaknesses. After this, Koji remains watching the rest of the matches.