Dousou Kai
English title: Yesterday Once More
Japanese title: 同窓会
Type: OVA
Episodes: 4
Source: Visual novel
Genres: Hentai
Studios: Arms
Producers: Pink Pineapple, KSS
Duration: 28 min per ep
Rating: Rx - Hentai

A young group of friends meet up for the first time in a very long time after finishing high-school. One of them remembers how once ago a girl left him Daisies and a love letter inside his locker, back in the high-school days. He has three suspects of who this secret lover could be and so there is only one way to know... by having sex with all of them.

(Source: AniDB)