Alright, my personal thoughts.
This game clearly takes inspiration from Wedding Witch. If not then you basically made a lower quality version with some variation in how mechanic work. I'm not gonna shame a small time solo dev compared to a small studio but I will say that if you haven't played Wedding Witch, I highly suggest you do for inspiration. Growing over 1 level based on upgrades is fine, but you have to make a lot of upgrade paths and make each path evenly viable. Additionally, I really suggest spending more time on making 1 good character with a lot of replayability than multiple AI generated designs with virtually no difference other than different webp gens.
It's up to you how to make things work, but if you stick to 3 paths of upgrades: muscle, breast, corruption (whatever that means), then each one needs its own line of power. Wedding Witch, for example, has large breasts as AOE damage, muscle is fast close range attacks, corruption is damage of time. Gaining things like HP, regen, etc, is related to pickups that spawn on the map or "relics" which are once per level. You could simplify this and have general perks like max HP at level thresholds like every 5 or 10 levels without blatantly copying another game. This way you can tweak xp systems and make each path a unique playstyle rather than forcing 1 everyone to play with muscle fetish just to max out damage. I have nothing against people and their kinks, but for me, seeing arnold schwarzenegger muscles on a big titty anime girl is instantly a turn off. You do you, no shame, but personally, allowing your players to decide how much they want of a path and not make them pseudo mandatory would cater to a larger audience.
Now to close out my review, my intention is to provide some ideas to make the game more interesting and cater to a variety of kinks rather than forcing 1 or 2. Obviously you can only do so much as is, the game is kind of one playthrough and then I have no reason to come back because I expect future updates to just be the same game with more AI pics. You've got a foundation, a small following of interested players, I really suggest spending more time making the game itself feel rewarding and unique rather than more AI pics. Alternatively, finish the game as is with the third character, then make a new version that fits a more roguelike style as that will drastically improve returning players. Hopefully you can make some money off the game and hire an artist to make 1 character with a variety of "enhancements" via layered images and then you have a really solid game idea. I wish you the best and hope to see more in the future.