Reincarnated in High school DXD {On Hiatus}

Y/n was a normal high school student. He was an introvert who just loves anime and manga. When ever he sees other people with their friends he always regretted not having friends. One day when he was walking from school to home, he saw a man with knife chasing a girl. He went to save the girl but he was stabbed in the stomach.
When he open his eyes he was in a garden. He looked around to only see an old man. How will his life be when he is reincarnated in his favorite anime world?