Mikasa seems to be a sweet young man but he is also a very skilfull sniper working for the company called Rakuen (Paradise). One day, a Rakuen's solicitor brings an old woman Kahoru to their office. She comes to kill Ei, a rival in the love triangle in the past. As they explain how to kill her, she gets very excited and begins to insist she has to do it by herself, and asks them to train her. She is so insistent that finally Mikasa agrees to train her. Despite the expensive fee and hard training, Kahoru never gives up. Meanwhile, Takashi, a man who as been suspicious about the death of his sister, reaches to Rakuen and Mikasa...