
Kosei Tsuburaba trained for a hero license as a Class 1-B student at U.A., turning his own breath into invisible barriers with the Solid Air Quirk. Competitive and loud about it, he is nonetheless valued as a backup player rather than an attacker. Eight years past the Final War he has graduated and works as a Pro Hero.
Kosei's eyes are oval and dominated by large pupils. His hair, auburn to begin with, is short and juts up in uneven spikes.
For hero work he wore a plain light blue jacket with a high collar and lighter accents across the shoulders, a black shirt beneath, pale trousers with gray kneepads, and heavy brown boots with cylinders built into the soles. The costume he wears eight years past the Final War runs dark blue and adds accessories at his sides; by then he has taken to yellow glasses and dyed his hair blond.
Enthusiasm and competitiveness drive him, and he sets a bar for himself that keeps him from sinking to a rival's level. That standard has its limits: after shutting down Katsuki Bakugo with his Quirk, he could not resist taunting the Class 1-A student, and like Neito Monoma he is content to settle for less rather than chase the top spot.
Within Class 1-B he is counted among the common-sense kings alongside Hiryu Rin, Yosetsu Awase, and Sen Kaibara, which marks him as one of the calmer heads amid his class's antics. Offense is not his lane; descriptions of him land on a strong support player whose Quirk makes everyone else's work easier. A quietly lecherous streak surfaces occasionally, and captured by Tsuyu Asui, what occupied his mind was mostly the sensation of her tongue coiled around him.
Solid Air: Exhaled air hardens at his command, letting him raise invisible walls and platforms that hang in place even under a person's weight. How large they can be comes down to his lung capacity. Early on the barriers were fragile, and Katsuki shattered one with a bare fist as though breaking glass. Kosei improved the Quirk afterward, and his walls reached the point of needing repeated blows from metal pipes to give way. The hardened air also blocks sound, which makes it a counter to Quirks routed through the voice, Anivoice and Brainwashing among them.
Air Prison: Refined after the Quirk Training Camp, this technique sends out squares of air that he assembles into a box around a target. Koji Koda was held inside one long enough that Jurota Shishida struggled to contain his strength afterward, which speaks to durability well past his earlier work. He unveiled it during round one of the training event that set Class 1-A against Class 1-B.

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Kosei Tsuburaba's Quirk is called Solid Air, which hardens his exhaled breath into invisible walls and platforms strong enough to hold weight, with the size limited by his lung capacity.
Solid Air belongs to Kosei Tsuburaba, a Class 1-B student at U.A. High School who uses it to build invisible barriers and platforms in support of his teammates.
My Hero Academia never confirms a romance between Kosei Tsuburaba and Tsuyu Asui, though the wiki notes a quietly lecherous streak in him, including a moment after she captured him where his mind fixated on the sensation of her tongue.
Kosei Tsuburaba is enthusiastic and competitive, valued by Class 1-B as a level-headed support player, though he cannot resist taunting a rival once his Quirk shuts them down.
Kosei Tsuburaba's signature move is Air Prison, which assembles squares of hardened air into a box strong enough to contain a target.
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