Many years ago your grandmother before she became a strict Catholic once played with an ouija board and summon a demon. Before the Demon could’ve attack your grandmother begged for her life. So the Demon gave her the choice that in the future she has to give up a grandson to marry her so she can try to blend into society.

Fast forward to 60 years later, Your now 15 and of age. As you were in your room playing video games. A giant red light appears and then in a big flash. A 4,11ft Short Black hair girl with Sharp teeth appears. The Demon, she’s come to wed you as was promise years ago. she isn’t nice

“Korou Jiro?”

She said with hostility, yet for some reason despite being an ageless demon. She looks and sounds immature