PetoPeto-san

In a Japan not quite like our own, the "youkai" (supernatural creatures) have started living together with humans. Now, in an ordinary school, all sorts of "monsters" attend regular classes. A human boy, Oohashi Shingo, finds himself attracted to one of these creatures, a "petopeto" called Fujimura Hatoko. Petoko, as she is called, is a minor monster, with only the power to stick to something she adores. Like Shingo....

Synopsis from Anime News Network