Kosei Tsuburaba

Sports Festival Arc
He teams up with Neito Monoma along with 2 other Class B students. When Katsuki attacks from above, Neito warns him about the danger, causing Kousei to create a solidified air wall, which stops Katsuki. However, Katsuki breaks the wall and grabs two of Neito's headbands.

Quirk
"Solid Air"- Kousei's Quirk allows him to solidify air to form a wall or platform. The size of the wall or platform depends on the lung capacity.

However, It seems that these walls and platforms are not strong as Katsuki was able to break a wall easily with one punch.