Very simple yet engaging 1st person dungeon crawler RPG. If you're worried about getting lost despite the lack of a map, don't be since corridors are pretty linear with just enough room to find optional goodies.
Encounters are all scripted and the combat is similar to Resident Evil Gaiden (or I guess Undertale for the normies out there) where attack/defense is dictated by timing a button press on an action bar. Each fight with the monster girls rewards you with a simple H scene and some gold, which can be spent at the store. There's some risk/reward for how you spend your gold, with healing items being fairly impotent compared to the volatile yet expensive fire scrolls.
The lore is found through tombstone inscriptions found out of order, which you get to piece together sort of like a Souls game. It's perfectly serviceable and helps you sympathize with the final boss, so its inclusion is a win in my book.
Ultimately it's a fun and short romp with some cute H scenes. The game isn't terribly difficult and there are some fun twists here and there. If you find yourself stuck, don't feel bad about starting over to redo your spending a bit better since it's a short enough game that restarting won't ruin your day.