One day, Tatsumi, a lonely man working in the underworld, encounters the murder scene of his ex-girlfriend Kyoko. Tatsumi barely escapes with Kyoko's younger sister Aoi, who was with him. Meanwhile, Aoi, who has lost her beloved family and swears revenge, pursues the perpetrator of Kyoko's murder. Despite his hostility towards Aoi, Tatsumi ends up accompanying her on her journey for revenge.
