When Okumori Rei was in middle school, in order to protect his mother, Shoko, from DV, he killed his father. His father's death was treated as a missing person case and became a secret between him and his mother. Although, Okumori Rei spent most of his life thinking, 'I don't need friends or a lover', he meets and falls in love with Tachibana Sawa. He then decides to marry her. However, soon after his proposal, someone that knows about his "secret" starts sending him eerie messages...!?