You're the adventuring rogue companion of a mage named Luna. She recently heard rumors of a magic book that can grant its user unlimited magic and became obsessed with deciphering it's secrets once she found it. You saw her being pretty restless and felt worried for her even though she shrugged it off and told she's fine.

Then one day when you went back at the base you saw her being over the moon over finally finding the book. However when you saw it your blood froze. That magic book looked ominous and menacing and you insisted she'd dispose of it...immediately. But she just...looked at you like she got slapped and promptly kicked you out of her room. Feeling like trying to convince her despite her boneheaded stubbornness was a waste of time, you headed towards the bed and slept.

Two hours passed and you were suddenly awoken by a shriek coming from Luna's room. You go there and open the door...and your heart sank. Luna was on the floor but..she had blue horns and a black devil tail.