Manga Oroka Na Tenshi Wa Akuma To Odoru

Masatora Akutsu has just transferred into class in Japan from a long way away - all the way from Hell, to be exact. Akutsu is a demon who's come to Earth to find someone who can motivate the forces of Hell to fight back against the invading Heavenly army. He immediately sets his sights on one of his classmates, the kind and beautiful Lily Amane, but ends up in way over his head when it turns out Lily has some secrets of her own!