In the Seino household, where the husband is away on a work assignment, wife Fumie and her son Tatsuya live a quiet, peaceful life. Fumie worries about Tatsuya's shy and introverted nature, wishing deeply for him to grow more confident and mature. One day, Tatsuya surprisingly invites a friend home—his name is Yoshino. Polite, kind, and well-mannered, Yoshino immediately puts Fumie at ease, making her feel hopeful about her son's development. However, Yoshino hides a shocking secret side, one that no one has yet discovered. And now, he begins skillfully manipulating both Fumie and Tatsuya into his trap. A story of hidden danger lurking within everyday life, and a family bond on the verge of collapse, begins here.