I get what you're saying with the intensity thing. I tried to balance not ramping up too quickly, with my desire to do fun stuff in the first release. This is my first stab at making a game, so I'm still kind of figuring things out.
There will definitely still be a ramp up of intensity when it comes to the MC. I'm going to use your friend and his sister to showcase more intense content while that happens.
And don't worry, there will be plenty more watersports in the future. I'd say it's one of my top 3 fetishes.
It all depends on what you plan, in the end: (a) a "very big" game with a realistic story that explores how the people involved (especially the MC) change through time, as well as the interesting characteristics of the world they live in, or (b) a framework in which to show femdom scenes. Of course, (b) is a great thing (I thoroughly enjoy your animations, and I would enjoy them even without any story or context; they're just really good!), and I am curious about the range of fetishes and scenes that you would be interested in bringing to life in your game; but (a) is also very rewarding, if you are interested in investing the time and creative power that it takes.
From the (b) viewpoint, I'm curious about how many fetishes you would include. I LOVED the ass-licking scene with Irene, and the peeing scene with Julian's sister; I hope we'll see more of both! It would be great to have other kinds of worship, too (pussy licking, for instance; and, a favorite of mine, shoes or boot licking; I'd love to see the MC lick the girls' shoe/boot soles, especially if they are dirty). Personally, I am also quite extreme in my tastes (why limit toilet slavery to only pee drinking?...) and I would love to see the women being really, really, REALLY cruel to the MC; but I think your intentions are probably more on the mild side, and that's OK with me. It would be nice if the women could be more verbally abusive to the MC, insult him, give him insults as nicknames and make him answer to them, spit on his face, etc. Also, I'd love to see more women involved. Perhaps at some point Iris could go for a walk with the MC on a leash (perhaps on all fours), and then they meet various different neighbors, each of which requests a different thing from the MC (they ask Iris of course, never the MC, and Iris grants permission), and then the MC does what they ask (e.g., clear their shoe soles with his tongue, be a seat for them to rest, perhaps be a toilet, perhaps be a punchbag...) while Iris giggles and mocks him.
(A couple of technical details: why not have a skip option, or at least a CTRL fast-forward? A clickable gallery of scenes at the end, or as an option in the title page, would be great, too.)
Now, from the (a) viewpoint... Are you interested in really developing the world and the characters in a realistic way? If you are, I would say I have to agree with those who say that the story feels a bit rushed. Things happen too fast; the stuff that happens to the MC in day 1 should probably be spaced over several days, with more "normal" stuff happening in between. After all, well, just imagine: after a life in which nothing like that had happened up until the beginning of the story, the MC, in one day, is forced to lick his non-sister's feet, has a jar of ointment inserted into his ass, is forced to lick his non-sister's ass, and watches another guy drink his sisterr's pee... The spankings are probably more normal, but spanking the MC in front of his non-sister and then letting her laugh about his penis size probably should also add to the set of new things, as also was having to go out naked / with an apron to hang the sheets and then being ogled by the neighbor... All that, happening in one day, should be quite shocking, perhaps even traumatizing, to the MC. It would make more sense to space it, perhaps having the story jump weeks or even months between traumatizing events. Also, it seems the MC (judging by his dream sequence) also had submissive/masochistic tendencies that he either denies or is ashamed of; this could be used to ease his pain and slowly accept and eventually see as natural the things that the women do to him.
Also, what about the female characters? Iris seems to be naturally dominant; how come? Was she always like that? Or was it the influence of the world around her? Can you be made dominant just because the world expects it? Doesn't she have any internal struggles, is she just, you know, a means for the MC to accept his place? If you're interested in developing all characters, it would be interesting to make the women more complicated, perhaps also struggle with moral issues ("I like my non-brother but I also want him to know his place and lick my ass!... Is it OK for me to think like that?"). The conversation at the table with the non-Mom suggests that Iris got these ideas from her friends at school, but people usually don't just accept kinks because their friends talk about them at school if they don't resonate with something inside (perhaps conversations between Iris and her friends at school, at various moments in her life, could shed some light on Iris' evolution?) Also, why did the MC's non-Mom want to raise the MC and Iris as equals? Where did she got this idea, and how does it interact with the way this world is? What are her internal struggles? Is she a little bit against the inferior position of men in their society? If so, how come?
Which brings to mind the world itself: why is it like this? Why can only women use magic? Why did women, just because they had more power via magic, decide that they would be sexually dominant? How did the history of this world go -- did it begin like ours and then at some point women acquired magical powers (how?), or was it always different from ours and women always had magical powers there? How does their government work, what exactly is the social status of men, and how is it justified? How does it interact with their culture?
Of course, all these questions are important only if you are interested in developing all these details -- which is like asking if you're interested in making this game a little like G.R.R. Martin's "A Song of Ice and Fire" or Tolkiens' "Lord of the Rings" but with femdom. I.e., if you are interested in (a) above. If you aren't, and prefer just (b), that's fine, too. But since you asked for comments on the storytelling, I thought I could mention all these things in case they are interesting to you.
Good job thus far, and I hope you're having fun with the creative process!