Kosei Tsuburaba

Kosei Tsuburaba is a student in Class 1-B at U.A. High School.

Appearance
Kosei is a young man with short, brown spiky hair and large oval-shaped eyes.

His hero costume consists of a simple light jacket, with a dark shirt underneath and plain light colored pants.

Personality
Kosei is a very enthusiastic and competitive individual who tries to hold himself to a high standard as he makes an effort to avoid descending to the level of his rivals. He told Neito to stop provoking Katsuki Bakugo because he felt it was something the latter would do.

However, Kosei was not above taunting Katsuki himself after stopping the Class 1-A student with his Quirk. Like Neito, Kosei has no problem settling for less rather than aiming for the top.

He seems to have a subtle, yet lecherous side on him, as shown when he got captured and he was mostly thinking about how Tsuyu's tongue was wrapped around him.

U.A. Sports Festival Arc
Kosei Tsuburaba first appears at the opening ceremony for the U.A. Sports Festival. He takes the field with his fellow classmates in Class 1-B. He is able to qualify for the Cavalry Battle after taking twenty-third place in the Obstacle Race.

For the second event, Kosei joins Team Monoma with Neito Monoma, Sen Kaibara, and Shihai Kuroiro. After stealing Team Bakugo's points, Kosei urges Neito not to provoke Katsuki, because Kosei believes this is something Katsuki would do.

As the Cavalry Battle's time limit runs low, Team Monoma plans to allow the clock to run out and secure second place. However, Katsuki suddenly flies at them using an explosion. Neito orders Kosei to stop Katsuki using his Solid Air Quirk, but the latter punches through it and snags two of their headbands.

Other teams try to capitalize on Team Monoma, but Kosei and Neito use his Solid Air Quirk to repel them. While fleeing, Kosei reminds Neito that they're still in fourth place despite losing two headbands. Neito agrees to defend their remaining points to the last, but Katsuki strategically uses his teammates' Quirk's to close the distance between the two teams. Kosei tries to stop him, but Katsuki blasts through the air shield and takes Neito's last headband. The Cavalry Battle ends, and without any points, Team Monoma fails to advance to the finals.

Forest Training Camp Arc
On the day of the forest lodge trip, when Neito Monoma mocks Class 1-A, Kosei is seen observing.

When Class 1-B arrives at the training camp. Homeroom teacher Sekijirou Kan explains that they will be extending their Quirks and that the more they use their Quirks, the stronger they will be by breaking their limits. After Class 1-B witnesses Class 1-A's training, Itsuka Kendo asks Shota Aizawa if can they observe everyone, he explains that is the reason The Pussycats are around.

After the Vanguard Action Squad start their attack, Kosei is one of the first students to be affected by Mustard's Sleep Gas, being carried by Todoroki all the time while he and Katsuki are fighting Moonfish, and chasing Mr. Compress afterward.

Joint Training Arc
Kosei, like the rest of class 1-B is part of a Joint Training with class 1-A. The rules are that one team has to capture the other team and imprison them. During the Joint Training, he is paired with Ibara Shiozaki, Jurota Shishida and Hiryu Rin. His opponents are Tsuyu Asui, Kirishima Eijirou, Koji Koda, Kaminari Denki and Shinsou Hitoshi. After Jurota incacipates Tsuyu and Kirishima, Kosei uses his new special move, Air Prison, to trap Koji, rendering him completely defenceless. Kosei then climbs on Jurota's back and tells him to attack the rest. However it is shown that it was not Kosei speaking, it is Shinsou's new gadget, the Artificial Vocal Cords, that allows him to sound like anyone he wants. Shinso then tries to use his Capturing Weapon on Kosei and Jurota but Kosei manages to trap Shinso with his airprison in time. Kosei then snaps Jurota out of Shinso's spell with a slap to the head and tells him to attack, while pondering about Shinso's quirk. Next Kaminari goes for an attack on the duo. Jurota answers by smacking Kaminari into a wall but got shocked by his quirk but Kosei jumped off him in time to avoid it. However, Kosei is caught by Tsuyu in midair and sent straight to their jail. While in his prison cell, Kosei is excitedly thinking about how her he was almost entirely wrapped up in Tsuyu's tongue.

Quirk
Solid Air: Kosei's Quirk allows him to solidify air to form a wall or platform. The size of the wall or platform depends on his lung capacity. However, it seems that these walls and platforms are not strong, as Katsuki is able to break a wall as if it were made out of glass using only his bare fist, and his fist did not look injured in the slightest, this weakness is overcome after much training.

Super Moves

 * Air Prison (エアプリズン): Kosei refined his quirk since the camp arc, and is able to send out squares of air, and shape them into a box to imprison his opponent. He displays this ability in the first round of the Class 1-A vs 1-B training event.

U.A. Sports Festival Arc

 * Team Bakugo vs. Team Monoma: Loss

Neito Monoma
Kosei and Neito appear to have a friendly relationship. During the U.A. Sports Festival Kosei went along with Neito's plan to throw the qualifier. He also joined Neito's team for the Cavalry Battle, during which, he was the only teammate to voice his opinion on Neito's actions.

Trivia

 * His name contains the kanji for "circle" (円), "place" (場), "hardness" (硬), and "formation" (成).