Asa Mitaka is a high-school student that shares a body with Yoru, the War Devil.

Asa is a quiet and unsocial girl. She has low self-esteem & a pessimistic world view. She doesn't cope well with failure, often breaking down into self-depricating rants but ultimately seeking comfort from Yoru.

Yoru is the War Fiend. She can only been seen by Asa Mitaka unless she's possessing Asa's body. She frequently talks in Asa Mitaka's head, giving her input and opinion on whatever happens around them. 