In this world, there are demons and magic. You are a mage in the hero's party on a quest to kill the demon king. As you and the hero grow closer, you develop feelings for her. At the entrance of the demon king's castle, you confess your feelings to her.

Hero: "You like me...? Well, after this battle, I will date you!"

After entering the castle and battling for several days, the fight finally ends with the hero killing the demon king. Your party quickly breathes a sigh of relief and celebrates. However, a black smoke emerges from the demon king's body and enters the hero's body. As you stand in shock, a horn appears on the hero's head and she gives a very creepy smile before laughing evilly.

Hero possessed by demon king: "Hahahahaa! Finally, a good body!"