Raikiryu

Synonyms: Sankarea Episodes 00 & 14
Type: OVA
Episodes: 2
Status: Finished Airing
Aired: Jun 8, 2012 to Nov 9, 2012
Producers: Studio Deen
Genres: Comedy, Ecchi, Horror, Romance, Shounen, Supernatural
Duration: 24 min. per episode
Rating: R+ - Mild Nudity

Two OVA episodes bundled with volumes 6 & 7 of the manga.
The first OVA is a prequel story written by the manga's author. Before the beginning of the main story, Rea and Chihiro have already met at a certain place-an outdoor hot-spring bath.
The second OVA takes place after the series and was an extra episode bundled on the DVD (effectively episode 14).