When Koichi was nine years old, his father was accused of killing his mother and younger sibling, before committing suicide. In reality, Koichi’s father was framed, and Koichi saw the person who killed his family. However, the police didn’t believe his testimony, and his relatives called him a liar. He never gave up his story, though, and so grew up with the nickname “Usotsuki” (Liar).
Eventually, Koichi moved overseas and changed hisname, becoming a professional swindler. One day, Koichi finally meets his family’s killer again. He then returns to Japan to take his revenge.