Kenka Bancho Otome

Kenka Bancho Otome is a video game series that received an anime adaptation in 2017.

The story follows Hinako Nakayama, an orphan girl who one day finds out that she has an twin brother named Hikaru. Born into a yakuza family, Hikaru is expected by his father to attend Shishiku Academy, an all-boys high school overrun with the toughest delinquents in Japan where he is expected to beat them all up and become the 'bancho'. However, Hikaru would rather cross-dress and send his days having fun so he essentially blackmails Hinako to switch places with him, with her amazing fighting skills helping her fit right in.

Episode 12
Hikaru switches places with Hinako and bares his chest in order to continue fooling the others into thinking that she's actually him.