Tsubasa Inuzuka, who has been on the run for keeping a secret, promised to his beloved Natsumi to meet her again after a year. But before said meeting, Tsubasa sees a man who is about to jump off a building. By transforming into Inu Brother and saving him, his true identity is revealed to Sononi. Wanting to know more about human love, Sononi offers Tsubasa a bet. She asks Tsubasa if he can turn the darkness into light of said heartbroken man because of love to prevent him from becoming a Hitotsuki.
