Fun Fun Factory

Fun Fun Factory (funfun工房) is a shōjo manga by Yoshitomo Watanabe.

Story
Michiru Mochizuki and her friend Chiya Takekawa go together to a restaurant, the Fun Fun Factory, where Michiru eats a dessert to celebrate her birthday; later, when she's singing a song which she heard from Sonou, the restaurant's owner, cakes start raining from the sky. As it turns out, Michiru's dessert contained a witch berry, and poor Michiru is now cursed and possessed by a witch. That not being enough, associated with the berry are 10 star grapes, and the ten young boys who ate them become cursed as soon as they enter in contact with Michiru and the witch inside her.