Living as the daughter of a rich family, Oto's life seems to be the perfect one. But it doesn't take long for it to shatter. Her father runs away, leaving Oto and her mother behind after his company goes bankrupt. Nevertheless, she continues to attend Eitoku Academy, hiding the financial status of her family. After Haruto, the leader of C5, finds out about her status, she wants to change schools. But she can't do that as her engagement with Tenma depends on her enrollment in Eitoku Academy until the age of 18.