Hijikata Toshizo (土方歳三)

Hijikata is the Vice-commander of the Shinsengumi and makes most of the Shinsengumi's decisions. He is called Oni-fukuchou (Demon Vice-commander) and is both feared and respected by his men. He is also often referred to as "Toshi" by Kondo. Hijikata is the one who brought Chizuru back to the Shinsengumi headquarters the night she witnessed a Rasetsu on the loose that attacked two men chasing her. He is responsible for her welfare, and even though he acts as if this were to his dismay, he cares for Chizuru's safety, and is often shown protecting her during battles. Hijikata drinks the Water of Life and becomes a Rasetsu in order to defeat Chikage, fueled by rage after seeing fellow Shinsengumi warrior Genzaburo Inoue dead. Even though Inoue had been killed by Satchō warriors (Satsuma-Chōshū alliance), Hijikata takes it out on Chikage, starting a duel as Chikage goads him.

Referance:
https://hakuouki.fandom.com/wiki/Toshizo_Hijikata
https://en.wikipedia.org/wiki/Hakuoki#Main