From Sapphire Sky:

Saijou Kiki is a model and child star, but with the release of her new commercial, her popularity skyrockets. At school, she harbours feelings for Takumi-kun... but she somehow ends up kissing Teppei, his friend?! And what's more, they've switched bodies due to some sort of old legend?!



From Chibi Manga:

Everyone is talking about Saki since she acted in her first CM.

She's in love with Takumi, who's in the neighbor boys high school: Sashirou High school. One day, she fell in the stairs and incidentally kissed Teppei, a student of Sashirou High School. That's a big shock! but something started to change inside them...