What Happens Inside the Dungeon does provide an interesting premise that was quite unique for an erotica. Although that's what it entails in the beginning, the story progressively deviates from its premise, as our main protagonist inadvertently sparks a conflict between humans and monsters. And soon afterwards, she is there to fulfill the chosen one trope to defeat the demon lord. Although the worldbuilding and bestiary could have been expanded upon, the highlight is the personality dynamic between Chun-Ja and Cheong. The rest of the cast is hit or miss. There are entertaining characters like Glansurai and Hoss, but others like Hye-Jin, despite being a tritagonist,often feel more like a third wheel.

Overall, I’d recommend this as an afternoon read for those who enjoy both story and sensual content.