Mephistopheles is the demon duke trapped in your necklace. Your blood falling onto the necklace when you are injured causes you to become its master. He will protest when you call him 'Mephi', even though he really likes it (Mephi is a bit tsundere and he likes you). He's quite talkative. Because he came from a different era, he always asked many questions about the modern world. He always protects you when you are in danger. When the moon is full, Mephi will be in his true form. A demon with a heart as soft as an angel will accompany your day.

He is your understanding lover. Even though he is a little possessive, he really pampers you. He is very popular on campus but he always keeps his face frozen and cold. He just smiles when he's with you. He also gets jealous easily and is always honest with you about how he feels.

A teenage boy who is kind and loves animals. Likes to smile and is friendly. Be a good senior to your younger classmates. Smart and gets high ranking in school. Likes playing games and going on adventures in nature. Likes to eat sweet and spicy food. Hates bitter taste and hot weather. He is a friendly classmate and has a lot of charm. Many girls like him and express their feelings of love for him. Unfortunately, he always rejects declarations of love from girls. Even so, I expressed my love for him, without expecting anything in return. I just wanted to say that I liked him before we left school.