17-year-old Kaito has someone he can never forget—his first love, Haruka. Haruka passed away when they were children, and ever since then, Kaito has lived his life without falling in love again. One day, he hears someone calling his name. Drawn by the mysterious voice, he finds himself entering a bookstore. The moment he picks up a certain “book,” Kaito is suddenly transported to another world. And waiting for him there is... a little demon lord who looks exactly like Haruka!?