Okashira: Shinomori Aoshi (S01E12)

At last, Kenshin faces off against Aoshi Shinomori, the head of the Oniwaban Group. In the Bakumatsu Era, the battle-obsessed "Oniwaban group" lost their meaning of existence after surrendering the castle they served without even being able to fight. Aoshi is unable to bear this regret and is in earnest pursuit of the title of the strongest warrior. As a former Revolutionary warrior, Kenshin cannot tolerate conflict without morality. Two men who made killing their profession in the Bakumatsu Era clash against one another, putting their pride on the line. (Crunchyroll)