The perverted serial killer who shook the world, "Shinagawa Piero," has been arrested. The killer turns out to be a 20-year-old woman! A boy, seeking to find his murdered father's missing head, writes a letter to her in prison under the name of Arata, a child welfare center worker who was counseling him. To fulfill the boy's request, Arata meets her, but when she realizes Arata did not write the letter, he abruptly proposes marriage to her to capture her interest.