Kane, a wandering adventurer, passed through an area known as the “Dragon's Lair.” After rescuing an old man being attacked by monsters there, it seemed the old man wanted Kane to subdue the monsters emerging from the “Dragon's Lair” and attacking people.

The old man possessed a “Hypnotic Magic Crystal,” an item capable of hypnotizing and controlling weakened monster girls in battle.

Controlling the monster girls should make the other monsters calm down, he explained.

Kane took on the task of monster extermination until the old man's injuries healed and was entrusted with the “Hypnotic Magic Crystal.”

Miria, the old man's granddaughter, decided to accompany Kane to ensure he didn't run off with the crystal, which was also a memento of her deceased mother.

And so, the merciless punishment of the monster girls began.

[From Official website]