Bio: The New Wind of Creation (Edited)

This story tells the point of view of Shidou Hyoudou, the adoptive brother of Issei Hyoudou. Everything followed normally until one day his brother had got a 'girlfriend', when he saw her, he had a strange suspicion about her and follow them on their 'date'. He come across a scary situation in which the girl reveals herself as a fallen angel and tries to kill his brother, although Shidou tried to protect him, the two died. However, the two of them wake up the next day and feel that them are no longer the same as before, heading into the supernatural world.

Note - I am not the owner of High School DxD or any of the characters, the entire credit goes to the original creators.