I liked it very much, but a few small quibbles:
the woman in the armor, Lily - she gets a slot on the title screen like she's a main character, but doesn't show up until very late in the game and has almost no content with the MC. Second, when she takes a shower, her entire character model drastically changes for that one scene.
With Alara talking about having MC's children, that seems like it would provoke a similar conversation with Erica. Also, MC pretty much always cums inside his lovers, and contraceptives beyond the occasional herbal remedy would have long since run out / expired (medicine's got a shelf life). Shit, the lesbian couple with the pregnant partner even hint at MC having the option at some point in the future. It feels like pregnancy / impregnation content was planned and just never followed through on.
It's practically begging for the MC to tell Cherry about the "magic particle" after he learns about it, since she's working on a "cure" that may or may not interfere with Syn's plan. And as she's a geneticist who wanted your sperm sample, it seems like Erica and her would discuss whether, given her partially transformed state, she's able to have healthy children or if they'd be born monsters.
In short, I enjoy it a lot but it feels slightly unfinished because there's a lot of dangling threads left, which could easily be solved by having Syn require a few day's prep instead of one, giving the MC time to discuss what they've learned with the major NPCs.
Also needs more breeding and at least some monster-fucking.