Nuki Doki Tenshi to Akuma Battle Episode 1

Angels and demons had fought over a long time to see who reign supreme. In order to bring closure to this feud, an angel named Sera and a demon named Firika were sent to the human world to finish this competition by contending for the love of a human named Yamato. Thus, Sera and Firika compete to for Yamato's love and the supremacy of their entire race, through any means necessary.