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.

Personality
Kosei appears to be a composed individual who tries 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.

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.

School Trip 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.

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.

Air prison (空気刑務所 Kūkikeimusho). 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 1A vs 1B 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).