Thanks a lot to everyone for this great thread! Making sure none have been mentioned before using the in-thread search but sorry if I included some I shouldn't have...
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by KISS (can create own scenarios, has a fuckton of DLC/addons, 2D STG (slave-training game)+VN, all characters including the MC are fully moddable to a crazy extent for a very old C game, can easily remove all males and monsters)
The "MC", Nano, is 100% lesbian and wants to create a 100% purest form of love world too, however very high caution is advised as it involves tentacles and futanari, some of which are very hard to forceskip. Pure love route confirmed to be 100% doable with both the storyline (Nano's lover) and the slaves you create (for interrogation or breeding purposes).
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by MBS Truth -Cherish Pink-: 2D VN, 100% females, togglable fourth wall breaking cum (can also change cum color, which amusingly affects urination scenes)
An absolute must. Akira, the MC, has an ultimate goal: as a titty addict (fuck's sake, I can't possibly be the only lesbian into flat females and desperate for adult flat females, especially vampires, succubi or various monster girls!), she wants the Ultimate Breasts and her very own Breast Harem. Even if you're not into big, fat tats, this is a nice one because Akira's one hell of a soft yet crazy psycho lesbian. No futanari, no tentacles, no dicks. Remember to turn off the "click here to ejaculate" option to avoid bukkake... unless you can mind-filter it into squirting.
Magical Girl Riru by Skunks (art by Yace/Usagi Mitsumata, link may not suitable for the zone due to rule 7) - 2D RPG, females only (has some tentacles and exactly one Mara-like monster, but no futanari, dicks or dick growth), vore(!), unbirth(!), some farting(!)
100% lesbian and get-raped-by-females. The antagonist being a skunk girl, well, there has to be some farting. Plus, it's a Skunks game. If you want to play a magical girl and a kunoichi and win (sometimes) or lose (often) to cute monster girls, this is a must.
Attack on Giantess - World Defence Force (art by kazo(!!!), unsure about link unless we already have it here) - 2D RPG, giantess/minigirl, vore(!) and farting(!)
Luna has a 100% lesbian route. Get raped by females, defend the world from absurdly thicc giantesses or (most likely) die trying. Legendary for being a game drawn by painter-level legend kazo, which also is one of the only works where kazo had to draw scenes with a male character. This also means the art is extremely enjoyable. The dialogue and story aren't bad, either. The artist has (lesbian!) voice works out under the kazo lab maker label so remember to check them out if that's your thing.
Skunks Pro Wrestling by Skunks (various artists, rule 7) - 2D RPG, farting(!), girls' pro wrestling, "incest" (sisters), tribadism
"Plot" is 100% lesbian but there's a crossdresser among the enemies. Other than that, facesitting and farting. A lot of farting. Some sisterly scissoring is always good!
Battle Fuckers by Skunks (art by Yace/Usagi Mitsumata, again rule 7) - 2D RPG, farting(!), girls' pro wrestling
Lise's route is 100% lesbian and she's super cute. If you're satisfied with facesitting and farting, this is a must. See above games.
Majilesca by SangO: 2D RPG, 100% females, not a single dick whatsoever, not a single male either. The catch? Rule 7 and scat, lots of scat, if you're not into it, you'll want to pass. Also very heavy censorship.
Free game by Sango. A trial version (yes, a trial of the free game) is available on the artist's twitter (as well as promotional videos). Momona and all of her monster girl friends and foes just are adorable, the game style itself is super cute. Strong female domination, full female POV, urination, also has you (the MC) grow into a crazy perverted monster girl as she advances and collects more Majilesca world lore on other species. Plenty of scenes and minigames. Can easily spend 20+ hours on the trial alone. Lots of dialogue and the dialogue uses a custom font and interface, so make sure you are fluent in Japanese. Due to the game background, it's all kana.
Hope all of these match Onibaku's criteria! Tried to include fetish warnings wherever I could. Feel free to remove whatever is out of place.