Akuma no Tenshi. Tenshi no Akuma.

Here in two dimensions separate from the living world was a Goddess who wanted Demons and Angels to get along. She put her hands together and made a dimension that was heaven and Hell combined...but what happen wasn't what she wanted. This dimension was like death itself...Painful. Its name is Aerai. The Goddess died and gave her wish to her daughter who was a human. Her daughter died and went to heaven. She fell in love...only to die again. She fell into hell after this she found out she was pregnant with an Angels children...one of the children was a demon the other an Angel. Amn and Am, Am wasn't strong enough when he was born so his soul was put into his brother Amn's body. They're cells split making it so t was half Amn, Half Am but some cells got lost and now Am is an angel demon and Amn is a Demon angel. Amn looking like a demon but acting like an Angel. Am looking like an Angel but acting like a demon.