High School DxD

A new student steps up to the gates of Kuoh Academy junior division. Zekka, a descendant of Miyamoto Musashi, wields the sword-shaped Sacred Gear "Tensei." Her goal? To make friends at Komaou Academy!? A new "DxD" series begins, guided by unique friendships and by Rias and the other high school students! (Source: Kadokawa, translated)

Hyodo Issei is a (perverted) high school boy. When he goes out on a date with his first girlfriend Asano Yuma, he is killed by her. Her true identity is Reinare, a fallen angel sent by a secret society Grigori to eliminate dangerous divine weapons. Issei is reincarnated as a devil by his senpai Rias Gremory, a Duke of Hell. Issei serves as Rias's low rank devil and fights against the fallen angels.