This is one of these games where people leave five star reviews saying "This has so mooch potenshul!". POOTENSHUL is certainly there, and at least this one is pretty likely to actually be completed.
I personally didn't have much issue with the combat, but by god choosing RPGMaker for this game was a massive mistake. RPGMaker absolutely hates smooth transitions and menu element animations like this game is trying to pull off, and it hates even more when they're piled on top of separate gamemodes requiring a ton of custom scripting to make function.
This should have been a Unity game, everything is omega laggy and I've seen many loading issues where some layers of the Imouto or the background dont load, which serves as a surprise horror fuel.
All text lines being voiced is a nice touch, although I have my reservation about the choice of the voice actress. I feel like the character she is trying to play doesn't quite suit her voice and the strain is audible sometimes.
At least blowjob and fingering are present in the CG files, but they are both gated behind molesting Imouto when playing shadowsouls with her and doing so more than three times makes the game explode in current version.
Night molestation someone mentioned being integral to imouto cohabitation genre DOES have UI elements made for it in the game files, just no artwork, so it will likely come later down the development.
I'm sure the current bugs can be ironed out and the content will get filled in. However, I cannot see the game performance improving at any point in time. It is not entirely impossible that the developer might end up forced to switch engines after all.