Wow. There really is just absolutely nothing to this one, huh?

What we have here is an extremely bare-bones idle game - I'm hard-pressed to even call it a Clicker - that mostly amounts to ever-increasing wait times that exist purely to try and get you to buy time skip boosters so you can get to the next monster girl summon and have a new JPEG to stare at. You buy assorted units (that feel like they have nothing at all to do with what you're actually trying to accomplish) which generate gold and mana at regular intervals as indicated by plodding progress bars. Units get upgrades at certain benchmarks, but you don't have to buy or prioritize these in any way, and so much information is obscured from you that there's no real determining the best use of your resources at any given time anywhere else either.

The only thing you can really do is fondle your monster girl of choice in various ways to effect the speed of the bars, and every few minutes doing so enough will trigger a sort of fever event where any bars that tick over give boosted rewards and you aren't punished for pervert-touching. There's a couple items that drop rarely; one shows you the resources per second a unit is earning for a brief window (which is only really any good once for realizing what your clicks actually accomplish), and the other lets you naughty-touch however much you want for a minute or so and thus make the bars go faster, because apparently your 200+ slaves (the first unit is slaves, btw) are encouraged to work extra hard when master gets to touch a boob.

If you check in even remotely often you will never be pressed for resources to progress. By the time the wait times on the summon materials clicked over I always had well more than enough magic to hit the button and barely feel a dent, and by the time said materials start costing anything too wild the wait times for the cheaper ones mean you'll have a week to scrounge up half a day's worth of gold and order the stupid things. You can send units to speed up the wait times a bit, but that costs you resources and the haste gain is slight at best (if it were any good, you'd have no reason to buy the time boosters, after all).

Your primary reward for progressing is scenes between the girls and the Summoner you play as from the latter's perspective, but this dude is a total dweeb who's written like some creepy incel who's never seen an actual woman before. It doesn't help at all that some of the early girls are innocent to the point of child-like, so you really get to feel like you're in the shoes of a creepy predator who'd definitely be a sex criminal if he could just stop having a heart attack any time a girl makes eye contact with him. A non-insignificant part of whatever counts as "lore" in this situation is that monster girls are all collectively addicted to / desperately desire / need your goo, just NEED it, though it is never expressed why and thus we're left to just assume it's a thin excuse for an author who feels like he needs one to be horny on main.

Something like two-thirds of these bizarre visual novel sequences are locked behind a separate 18+ patch you need to nab off the publisher's website, with the primary benefit of their presence being access to a whole second JPEG and its variants, which largely just depict an ever-increasing amount of mess as every interaction this dork has seemingly ends with him going off like a fire hydrant all over the place even when that seems physically impossible. (For the record, said mess isn't even drawn in a particularly appealing way; I hope cottage cheese turns you on.) It seems like every other scene has one particular description of what the girls are doing near the end that really betrays both the creator's absurdly specific fetish and lack of creative writing skills, and the surreal experience of realizing which phrase that is is the primary reason to recommend the 18+ patch to your friends so you can laugh at their increasing pain and feel less alone in this waking fever dream.

Anyway, within about two months with all of maybe 5 hours actually spent playing (you do not need to play as much as I have to do this; you could probably knock this thing out in like 3 honestly, and that's assuming you're actually reading the VN scenes and going for one of the Fever states when you check in every day or three), you'll have an easy 100% achievement rate for your Steam profile - and your proudest one, I'm sure - and jack else to actually do. Barring any last-second surprise after my two week wait for my last monster girl's materials to finally show up, there doesn't seem to be any rebirth / reincarnation system to speak of, nor any long-term goals unless you really, really wanna check in every month or so to see what the later production boosts are on the higher-end units. You are 100% here for easy achievements and the awkwardly written h-scenes that let you into the mind of a repressed 30-something virgin who sits in his intensely Christian mom's basement trying to imagine what a sex is like after having a wet nightmare where the serpent from the garden seduced him by wiggling its tail in his butt.

Monmusu is awful, shallow, and intensely difficult to recommend for reasons that aren't mean-spirited, and I still have no idea why I apparently need to own an entire town of people like some sort of Feudalistic noble just to summon an octopus woman to come slime my taint.