A Hero from another world defeated the feared "Demon King," and over time, people forgot about their fears and lived in peace. However, a mysterious creature named "Black Ooze" was born in a dilapidated mountain cave. Although it appeared to be an ordinary slime, it possessed a unique ability to absorb the abilities of the creatures it consumed. Its appetite grew as it absorbed the paralyzing poison of an insect and the knowledge and "desire" of a human. When a female mage entered the cave, it set its sights on her. Despite its dangerous potential, the world remained unaware of the new monster's existence.