Boku to Kanojo ni Furu Yoru

Sugamu Naito is just your average schoolboy. However, his life was changed when he was dragged into a battle between magicians called Makai Juutsushi. Naito was saved by a Makai Juutsushi girl, Yorumirumi. His meeting with her shook his lost memories. Now that he knows the existence of dark world, he was moved by something that was inside of him, and took a step into battle...

(Source: Baka-Tsuki)