Touken Ranbu Kai: Douden Chikashi Haberau Monora

Prequel anime to Touken Ranbu Kai: Kyoden Moyuru Honnouji.
After a defeat in Odawara, Yamanbagiri resigns from his position as Attendant. Heshikiri Hasebe is chosen to be his successor.
(Source: Crunchyroll)