Hotaruko - Season 1

Ryo travels back to her mother's home island following the woman's unexpected death. She believes the key to understanding her mother's unusual conduct lies in her origins there. Her mother had explicitly forbidden her from ever returning to the island or having any contact with someone named Hotaruko. Nevertheless, Ryo is determined to uncover the reasons behind her mother's bizarre sexual behavior. On the island, she discovers a hidden, dark cult dedicated to carnal rituals. This group ensnares unsuspecting women, brings them to peak ecstasy through seduction, and then offers them as blood sacrifices. Their brutal slayings are performed in devotion to their deity, Master Mizuno.