The Novel's Antagonist: I walk the path of a Villain - Chapter 43: The Possessive Girlfriend I once Had

Waking up, Kim Hajin finds himself in a familiar world but an unfamiliar body.

One day, I woke up only find out that I’d become a Demon Lord, an individual responsible for protecting a dungeon. The world I’d been spirited away to was one filled with violence. Gigantic monsters wandered through it and competed with each other each and every day for the right to survive. I had no choice but to strengthen my dungeon’s defenses in hopes of living another day—or at least that was what I’d thought. For some odd reason, I instead ended up spending my days in relaxation and bliss.

C-class mercenary. Started as a No Class, possessing nothing.

13 years of survival in the depths of the ditches.

I’ve managed to return to the beginning, but…