Senjuushi: Kijuushi-tachi no Happy Birthday!
Genres: Action
Type: OVA, Episodes: 1
Aired: Mar 6, 2019
Studio: TMS Entertainment
Source: Game
Rating: PG-13 - Teens 13 or older
Synopsis:
The story will be about the characters celebrating their master's birthday, which happens after the sixth episode. 

(Source: MAL News)