This review is made under the consideration of this game being the dev's first (released) work. TL;DR I consider this to be a decent-to-good game, rating it 3.5 stars. Here's why:
Art: 4/5
The art is pretty competent, with healthy, cute proportions and good shading. The inspiration from Fate/kaleid liner Prisma Illya's titular Illya is incredibly obvious, though. Sometimes the art is a little inconsistent (Yuki has noticeably larger tits during a BJ than in other scenes, for example) and there are some minor errors and oddities, but overall it's still good. There are 5 different ero ways for Yuki to pleasure enemies should the enemy's "sanity" value run out, all of which can be improved with practice and are voiced. There are also 5 defeat scenes respectively relating to the 5 bosses appearing every 20 days. I've certainly seen a lot less in some other devs' first games, especially with the Live2d animation in place here.
Music: 2/5
It's... there. Not bad, not really nothing special.
Story: 4/5
Yuki sees her parents murdered by a monster, but a Magical Girl mascot in the form of a black cat appears and helps her loop back in time 100 days so she might be able to avert this fate. Along the way, "Blackie" shows a surprisingly high intellect and interest in many topics, such as philosophy, music, and pop culture. The interactions between Yuki and Blackie are very cute and often amusing. I just wish there were more such discussion events. But being a roguelite card battler, there is honestly a lot more than I expected, since these kinds of games rarely ever even have a story beyond "Head out and defeat all the monsters."
Gameplay: 3.5/5
The part I consider the most divisive. On the one hand, there is actually a lot of competency in the variety of cards in play: many cards are unique in their effects, while others come in various strengths. They can be found from a selection after basically every battle, or bought in shops. The cards, in part or full, can also be improved via day events. Each card also has 3 slots (though initially the third is locked), and special events allow removing the skill from one card and applying it to another. This may raise the cost of the improved card, but sometimes also results in an overall more efficient version, and some combos are downright broken... On the other hand, being unable to freely sort these skills (or remove them if a mistake was made) can be a little annoying. Sometimes cards also don't improve despite the upgrade being applied, and this is very inconsistently applied as I have not figured out what, exactly, decides this.
Being a turn-based game, enemies appear from encounter events to trade blows. Unlike Yuki, who has an MP meter, the enemies generally have specific actions they take on a given turn, with bosses having far more variety than the mobs. As with Blackie, many of them reference pop culture and memes, or just spout incomprehensible madness. Some attacks even deal no damage at all. Some skills apply status debuffs such as the standard poison and burning (Yuki has these as well), but others are things like being bukkake'd, slimed, restrained by tentacles, or having vibrators forcefully taped in place. All of these actually do different things to manipulate and hinder Yuki, so it pays to hover over them and see what they actually do, since they can really screw with the player's flow if not careful.
Ero-wise, enemies have the aforementioned "sanity" meter. Its value usually doesn't go down unless Yuki's outfit is damaged, and if she's naked it will go down very quickly. Once the "Kibbolf" (I have no idea what that word means) state happens from 0 sanity, Yuki is forced into pleasuring the enemy in one of 5 ways. Initially this only means a handjob, but defeating bosses unlocks more ways. Every enemy is weak to exactly one of those, but it's also perfectly possible to just stick with your favourite (say, a BJ) to fill the resistance meter and escape.
