He seems to have a subtle yet lecherous side of him, as shown when he got captured and he was mostly thinking about how Tsuyu Asui's tongue was wrapped around him.
Solid Air (空気凝固,Kūkigyōko?): 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 very 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. The solidified air is invisible.
Air Prison (エアプリズン,Ea Purizun?): Kosei refined his Quirk since the Forest Training Camp Arc, and is able to send out squares of air, and shape them into a box to imprison his opponent. The fact that Koji Koda was imprisoned there for a while and Jurota Shishida had problems containing Koji's strength shows that these air prisons are much more durable than solid air he has shown previously. He displays this ability in the first round of the Class 1-A vs Class 1-B training event.
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