River's Edge Investigative Agency Okawabata

One day Muraki receives a request from the Director. About a week ago the Director was walking along the Sumida River after a night a drinks. Out of nowhere someone pushes him backwards, injures his forehead, and causes him to fall down some stairs. He wants Muraki to do background checks. Even after having constant surveillance on the Director day and night the mysterious figure can't be found. Then done evening the Director get a call from an unidentified man say he has kidnapped Megumi.