Well, i can review this demo and my issues with it in short version and long version.
Short version:
Game is balanced like shit.
Long version:
The number of enemies on screen is way too high, the waves of attackers that you have to deal with before progressing are too many, you can't get any currency or items from the levels unless you complete them and the aforementioned hordes of enemies also pay too little for the hassle of the grind.
The leveling requires way too much xp grinding and forces you to rely on shop exp items that are gated behind level tresholds and still cost too much.
The game basic systems are flawed and worse than other Umai Neko games and it shows its worst at stage 3.
No depth of stage so you can't sidestep enemies crawling on the ground and you can't dodge them by speccing in avoidance either.
Your attacks and animations are clumsy and slower than the speed at which crawlers spawn from both sides so you can and will be bounced continuously and then wiped by unavoidable animations on the ground as there are no invincibility frames for anything.
Even if you abuse the fact that you can't be stripped by these animations and somehow limp to the next part of the stage there are now standing enemies too and you have no hp to afford to tank even one hit and you will be hit as there's simply way too many enemies to handle.
Even special attacks won't help as they have weirdly shaped hitboxes that won't save you from damage since they too also don't have invincibility frames.
I could mentions minor annoyances too like the fact that the equip UI is clunky and that the stats are somewhat vague and too much shortened to understand well what they do at a glance but these are very minor gripes when compared with all the other roadblocks you face with this game.
In the end i will at least say that the equipment/outfits with a better UI and more variety could be a great addition to the dev's formula and the animations look somewhat smoother/better than what Umai Neko previously made, so not everything is bad but not much.
Over all id say that this game in the Umai Neko career is a step forward and two steps back.
If dev fixes the issues the game can still be good, otherwise i would suggest everyone to wait for a kind soul to post an hacked or complete gallery save and avoid wasting time on the fruitless grind.