Yoshino Takigawa, an ordinary teenager, is secretly dating his best friend Mahiro's younger sister. But when his girlfriend Aika mysteriously dies, Mahiro disappears, vowing to find the one responsible and make them pay for murdering his beloved sister. Yoshino continues his life as usual and has not heard from Mahiro in a month—until he is confronted by a strange girl who holds him at gunpoint, and his best friend a...