Satou-kun no Juunan Seikatsu(2005)

17-year-old Satou is part demon/part human boy with a facial expression set in stone. Enjoy his misadventures in the Makkai (the demon world) private high school as the only transfer student from Human world. On the first day of school Satou leaves a lasting impression on future monster classmates, and manages to tick off resident hot shot Grimreaper (aka talking bones), who's now dead set on seeking revenge for his humiliation - except when it comes to Satou things never go as planned...