Ultimate Gamer System: Factory Must Grow! - Chapter 29: Upgrades, people, upgrades!

One day I got a younger sister.Only I know her true identity.

It’s the vacation of a lifetime, a trip to a remote island filled with geniuses and murder.

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.

Bought it right away.