Yosetsu has long black hair spiked up and backwards, and rounded eyes. He usually wears a headband around his forehead.
Although he is not talkative, Yosetsu has a foul-mouth and is tense. However, in serious or life dangerous situation he is very easily startled and becomes much more talkative, while still being foul-mouth.
Yosetsu is very selfless, as he continued to carry Momo with him, even though the enemy was catching up with him, refusing to leave her behind despite her slowing him down. He is also willing to put himself in danger to fulfill a plan, despite showing fear.
He is also said to be very proud of his Quirk and confident in his abilities with it.
At the beginning of the event, Tetsutetsu's team attacks Izuku's team with Juzo using his Quirk to trap them, but Izuku uses his jetpack to escape. Tetsutetsu's team attacks them again, but Fumikage's Dark Shadow blocks them off. After the Human Cavalry Battle ends, Tetsutetsu's team fails to qualify for the final event. Tetsutetsu is confused as to how they lost all their points, and Ibara remarks that it is possibly punishment for taking Minoru's headband in such an unfair way.
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. When Class 1-B witness Class 1-A's training. Yousetsu is taken by surprise. Afterwards Itsuka asks Shota how they can observe everyone, and he explains that that is the reason the Pussycats are around.
During the third day, the Vanguard Action Squad attacks the camp, filling the forest with gas and fire. Yosetsu runs into Momo, and they are attacked by the Nomu, which injures Momo. Yosetsu carries her while running away from the Nomu, which cuts several trees down with its multiple weapon arms, consisting of chainsaws, drills, and hammers, to get to Yosetsu. Momo apologizes to him for dragging his speed down. The Nomu reaches him and is about to attack him with one of its weapon arms. Suddenly, its chainsaw arm stops and it retracts its weapon arms into its body and begins walking back to the Vanguard Action Squad's rendezvous point. Momo realizes that it is being called back because the villains have captured Katsuki. Thinking of a plan, she creates a tracking device and asks Yosetsu to weld the button onto the Nomu. He runs after it and bonds the device onto the Nomu's back. As it walks away, Yosetsu and Momo decide to continue running.
Quirk and Abilities
- In the Entrance Exam, he is ranked 10th place with 50 villain points and 6 rescue points.
- His name contains the kanji for "bubbles" (泡?), "torrent" (瀬?), "sea" (洋?), and "snow" (雪?).
- He likes mobile games.
- He bears a striking resemblance to Usui Horokeu from the manga series Shaman King.