Really cool first release. Great renders, sprites, animations, and nice little touches like letting you customize the 'relationship'. Excited to see how the promised clothing mechanic unfolds because attention to the m-sub's attire is something I wish a lot more games had. (Also very much hoping the teaser image for your $25 tier becomes a scene itself!)
You asked for writing feedback: overall I thought it was charming and managed to avoid some common lewd pitfalls. Setting up the player-character as a 'spoiled' outlier in a matriarchy is a great excuse for him to get into trouble doing careless/pervy things without making him seem like an idiot, and explains the chip of Iris's shoulder better than your average mean sister. It also works well as a player viewport since we're obviously not familiar with the 'real' workings of this world either.
I did find the harshness of Justin's treatment a bit distracting. Normally I can't get into matriarchy/female-supremacy settings (just personal taste) but some of the early scenes with Iris were warming me up (eg. if females really are a magical master race maybe the boys really are better off as subby pets under their control) but Sarah's scene broke that illusion.
If you want the world to be a harsh, hardcore femdom matriarchy where males besides the player-character (and eventually him, too) are treated like trash, that's totally fine, but it makes the implications that this is an 'otherwise normal world' (eg. neighbors, school, anime) see much more jarring and absurd (so I would maybe dial those back).
On the other hand, if Justin is intentionally meant to show the other extreme (ie. his family is unnaturally cruel to him), and most boys are somewhere in the middle between his abuse and your spoiled life, then everything is probably fine as is. I look forward to seeing how things develop regardless!
Line-by-line, Iris was a tad repetitive about you needing to learn your place before going out in the real world and how you're gonna be in trouble once mom leaves, so that could maybe be cleaned up a bit, but no major issues.
Cheers and keep up the good work!