The mysterious wizard, Cthu, is a kind-hearted person with a dreadful appearance. He bought a second-hand dungeon in the dark forest for a quiet environment to do his research. It troubles him, however, to find random adventurers break in his dungeon from time to time.

Cthu, who doesn’t want his home to become a haunted house, rescues lost adventurers every day while dismantling the deadly traps left by the former owner of the dungeon.

On this day, Cthu met a little girl, Luna. She was chased by the villagers for her magical talent. Instead of being intimidated by Cthu's dreadful face, the kind girl was worried that he would get into trouble and asked him to run. It moved Cthu so much that he suppressed the villagers with mind control, saved Luna, and decided to take her as a pupil.

Under Cthu's care and teaching, Luna's new life is colorful. She has learned all kinds of magic about mind control, and she has also made two friends of her own age. They are Beth and Little Troll. Beth and Luna have similar backgrounds. She was rescued by an apostate paladin when she was almost burned to death by the church. Little Troll and his parents had become the coveted target for hunters because of their unique racial talent, and he was the only one who survived.