Ai is a girl who worked at shinto shrine. She was raped and killed herself afterwards. Such incidents started to happen more and more frequently.
Two years later her sister Shiori starts to act as shrine maiden. Hero is former Japanese national sports player in shooting. He is asked to bodyguard Shiori, but Shiori gets raped and kidnapped on his eyes. He swears to avenge her and punish the offenders.

[From vndbreview]