Hotaruko
English title: Crimson Climax
Japanese title: 螢子
Alternative titles: Ho Ta Ru Ko
Type: OVA
Source: Visual novel
Episodes: 3
Status: Finished Airing
Aired: Feb 21, 2003 to Sep 25, 2003
Duration: 30 min per ep
Rating: Rx - Hentai
Studios: Arms
Producers: Green Bunny
Licensors: Central Park Media
Genres: Hentai

Lured to a cursed island by a carnal cult, victims are brought to the throes of ecstasy, then brutally sacrificed in a bloody occult ritual. When sexy Ryo visits her late mother's island home, she's in for a terrifying surprise. Can she escape with her life and her virtue intact. 

(Source: ANN)