According to the official website, an OVA of Itsuka Tenma no Kuro Usagi was announced to be bundled with the ninth volume of the novel. An animated crossover between Itsu-Ten and The Legend of the Legendary Heroes (Densetsu no Yuusha no Densetsu or DenYuuDen) fantasy story.
Genres: Comedy, Ecchi, Romance, Supernatural
Watch A Dark Rabbit has Seven Lives OVA episode 1 online — subbed and dubbed, with automatic AniList / MyAnimeList progress sync.