Tokuma de Yaru(2004)

Tokuma de Yaru

Early in the second semester after summer break, at prestigious girl's high school Seikou Academy, which the two twins Flare and Claire attend, a series of suicides begins occurring. That same weekend, serial inexplicable suicides begin occurring among the acquaintances of Tokuma Dearu, who works at the nearby video store. Every day, one person commits suicide without fail. Is this unusual incident really a chain of suicides, or is it actually a serial murder case? Tokuma, alongside his partner Shingo Yamazaki and the twin sisters search for the truth behind the affair.

Note: Book one of the Tokuma Series.