Kami-Sama Onegai! (Mio Junta)

From Yaoi Is Life:
Three months after third year high school student Aobane started dating his classmate, Takahiro, he is constantly worrying if Takahiro might get tired of him. Because compared to Takahiro, who is cheerful and popular, Aobane is shy and a poor talker. On his first shrine visit of New Year, he prays to the god of a little shrine that he could be with Takahiro forever. The next day, he found he has cat ears and a tail…?!