When a dungeon starts behaving strangely, aspiring Dungeon Keeper Aster steps in to unwind its troubles. After fighting his way through deadly monsters, he finds a young girl at the dungeon's heart--a young girl with a dungeon core.

Stella has just lost her mother, and on top of that, only now discovered that she, in fact, is the one who should rightfully control the dungeon. Overwhelmed and grieving, she shuts out humans... but one human still breaks through.

Together, Stella and Aster will find a compromise between human and dungeon, between the dark, monster-infested world beneath the earth and the bright, human-contaminated world above it.

But first... "Hey, will you be my dad?"

Spy X Family meets Dungeon Core!

[participant in the Royal Road Writathon challenge]