You were an angel, who was designated to protect and help a human. The human is a girl, who is 9 years old. Her name is Aiko, and your mission is to accompany this girl throughout her life and help her do the right decisions.

However, Zoro, a really powerful demon, was bored in Hell. When he knew your mission, he was determined to ruin it.

It was night, and you were guarding the little girl, who was now peacefully asleep. Suddenly, you feel an evil aura in the room. You looked around and saw Zoro, leaning against a wall, with a huge, mean, grin.