So let's start with the negatives. It's rough, it could use some fine tuning, more content and considering the translation's a bit half and half you will be confused without a guide. I recommend the starter guide to get the basis of everything. Some people report poor performance, no issue here but I have an i7-8700K and a Titan Z so, ymmv. I also recommend on a sale. Your playtime, unless you're *super* into wave shooters, love dress-up games, have specific fetishes or just really like that tactical butt (I do), will probably be pretty low.

However, for being what it is, it does it pretty decently. The game is a wave survival shooter game that has some freakish beasts running up to slap, smack and roll over you until you die. You can either jump right into the action with what you have through one door right near the spawnpoint, or go into a free-roam mode in the other that gives you time to put down mines, barricades, or turrets (with some miscellaneous other props) that you can reload, and then respawn to go back to the door to start up with some defenses. You get "CP", or points to spend for these things by either finding secrets in the world, doing the sniper minigame or just playing the wave clear and eventually dying. Recommend the sniper farmup, since it's easy enough for anyone to do and rather quick little minigame.
There's some hidden stuff that you can search for, side missions to complete and achievements to dig for. Each rewards you pictures/side stuff from the creator for viewing, but they don't do anything in-game. There's no over-arching story, just some tidbits and achievements you dig for yourself and piece together what the hell is going on yourself.
And yes, there's lewds. No, you won't have them hamfisted into your face unless you expressly go looking for them. Yes, they involve certain bodily fetishes. How that affects your interpretation of the game is entirely on your fetishes and preferred gameplay experiences. There's a lewder patch too, your choice; mostly removes mosaics and expands customize options.
You won't play for super long, since once you find out the exploits the game becomes super simple. Enemies are a bit rough on their hitbox and pathing so you can keep running circles on them pretty easy. You learn about which enemies to prioritize, and there's not a heck of a lot of variation in enemy types. You learn how to weakpoint them, and build up a barricade system in ideal places that lets you waveclear for ages. Eventually, you'll optimize optimize optimize your killing until it's a chore more than a game. I recommend a first run of Normal, and then immediately up the difficulty to Overkill, the best difficulty.

So TL:DR? Get on sale if you like a decent wave clear game, and know it probably won't eat up a huge amount of your time. It's rough, but the foundation is solid. I can see it being expanded on, and hope it is.
Also.
TACTICAL BUTT MOVEMENTS