Kedamono ni Lollipop

A high school student named Himari Kawashiro is assigned to help organize the school's cultural festival, a task she finds daunting due to her shyness and lack of popularity. While exploring an empty room, she discovers a cat eating sweets. When she approaches, the cat transforms into her classmate, Sennojou Shionji, who is wealthy, attractive, and well-liked, but also very arrogant. He reveals he is a half-beast who requires sugar to stay in human form, despite despising sweets. He asks Himari to keep his identity a secret. In exchange, she requests his help with the festival. He agrees, but only if she agrees to act as his servant at school. Their unusual arrangement marks the beginning of their story.