I finished it! I like Match-3 games, and as one of those, it kinda sucks. There's a couple of standard blocker-type tiles and some match-release tiles, but that's about it for variety. There's no power-ups, no skills, nothing to make the player-control side of things more interesting. A lot of the difficulty derives from speeding up the time limit, which makes a lot of late-game advancement rely heavily on RNG (looking at you Miss Valentina and Headmaster Kanna).
PRO TIP: press the circular arrow button on the bottom right the moment a board loads. It'll bring up the "Do you want to restart board" selection but, most importantly, it will pause the timer. Sure, it will obscure a bit of the board, but it will give you a moment to have a look for some good matches. Later puzzles will rely heavily on getting multiple-bonuses after multiple-bonuses so pausing using the restart menu to have a look at what else you can do as the match animations are happening is utterly vital to success. I highly recommend just restarting until you have a board that gives you an easy five or four tile combo to begin with, or a board that gives you an easy match for the match-release tiles.
Game mechanics aside, there are either grammar or translation issues here. A lot of them. It cheapens what little story there is. If you want to skip past it and go straight to the puzzle, again just click the 'restart board' button and press yes and it'll go right to it.
Porn-wise, the in-game sprites are better than the reward CGs (which seem censored, wtf?), and you can't even look at the sprites in the gallery.
So yeah. not good for a brainless match-3 game. Not even good for a fap. Go play Huniepop or Mirror.