A Conviction of Marriage

TMDB movie listing

Serial killer Shinju Shinagawa , called "Shinagawa Pierrot" for her clown makeup at arrest 3 years ago, remained silent during her first trial. Child consultation center worker Arata Natsume suddenly gets a request from Takuto Yamashita, the child of one of the serial killer's victims, who informs him that he's been corresponding with Shinagawa in his name in order to find out what she did with his father's missing head. Arata pretends to be an elite civil servant but finds that the Shinagawa he meets is different from the one he expected. When she realizes he isn't the sender of the letters, she goes to leave. In a panic, Arata, who never planned on getting married, blurts out "Let's get married!"