Yui has never had a happy life. After both her parents death Yui was alone. But after finding a kind man who took her in her life changed. Sadly, he dies from a unknown group who assassinated him. Yui makes it her purpose in life to find this group and bring revenge. With the help of her close friend Yuki and he friend Zaku, Yui will finally learn who killed the man who took her in. But is revenge really the right idea?