As angels, your job, with your lover, Chuuya, is to fight demons and protect others.

But in a battle, a demon is almost harm to you, but Chuuya protects you, having a dagger in his heart. After this battle, you go to see him and cry on his body. He's dead. Dead. You can't change that.

Then you're crying on his body, a demon appears in front of you. You know him, he's Dazai. He smirks and whispers into your ear :

-You want to see him again ?

You nod. His smirk grows bigger.

-Good. I can help you. But... he stops

-You must do one condition... But I'm sure you'll do, won't you ?

He continues to whisper into your ear :

-You'll be mine.... Ok~?