Sex: Prologue
Japanese title: SEX～Prologue～
Type: OVA
Episodes: 1
Source: Manga
Genres: Action, Drama
Studios: MAPPA
Producers: DMM pictures
Duration: 1 min
Rating: PG-13 - Teens 13 or older

The anime depicts an original story before Kaho arrives, when Yuki and Natsu have just met in Okinawa.

(Source: ANN)