Game's a bit janky, but it works.
At the beginning, you have a penis, three "tool hands", and tentacles. Funny enough, the tentacles are smaller than your penis. This is a boon because she can't take your penis in any of her holes at first, and the tentacles are the "gateway" to more.
Minor grievance that I think most people really should know and the game should've told you: cumming = stat points. Doesn't matter who or what cums, just cum a lot, anywhere. Dump points into more cumshots if you have to, and just go off like a machinegun. Don't bother with anything else for a while.
Anyway, it's one of those games where you fuck your sister, though the game doesn't really advertise that she is since there's basically no dialogue.
You can make both of you into a few species, something people don't seem to mention. Your options are human, elf, or "beastman" cat/dog (just animal ears + tail. The ears are the same for both though).
There's quite a few things to do with her, ranging from French kissing her mouth, to cumming up her pee hole (and swelling her bladder with gallons of cum), to letting parasitic tentacle things climb into her, to hypnotizing her into loving you, to stimulating her into lactating so much she becomes mostly-boob, etc. (No ass though, oddly.)
Most of it works quite well, though I've noticed there's no way to fill her stomach with anything, even if you cum 9999999 gallons of cum down her throat, her belly doesn't change.
There's a few little glitches here and there, I guess the only real glitch that might bug some people is that filling her womb with tentacle parasites doesn't actually show up in the x-ray; her womb just swells up empty, as if she's filling with air.
Dunno if it's a glitch or not, but the game's math definitely has something wrong; the gameplay starts pretty slow, carefully managing her wakefulness and her stimulation and whatever, but there's just this point where the numbers stop adding up and everything goes exponential, leaving you with thousands of stat points to spend.
I think it has something to do with HER arousal. You have a limit, she doesn't. As you do an action enough, it raises her stimulation of that part and she starts liking it more, but there's a point where you can pretty much touch that part and she'll cum. Instant cum = points. Feels like maybe the cum cooldown doesn't work as well as it should, since I later had one point where I was given 100k points to spend, heh.
(Almost forgot to mention: this happens to stretching too for some reason. One second she's struggling to take a finger, the next she's got a tree-trunk sized dick up her vagina.)
I'm an inflation nut, so here's my take on that part:
There's a lot.
A lot of inflation.
A damn lot of inflation.
She gets quite damn big if you fill her enough, I'm talking like she's got three beach balls under her skin and cum leaking from her pussy and nipples like she's literally about to blow up.
It's JUST her boobs and belly though, you can't forcefeed her or turn her into a balloon or something (haha).
Anyway, if you don't like cumflation/milkflation or giant hyperpregnancies, there's settings to slow/disable that in both the game's new game setting options, AND later on when you can get a lock/reset button for most stats, like turning pregnancy off but leaving cumflation.
All in all, neat game, but that exponential thing makes the game pretty short and easy. Still worth a play though.