TL;DR: It's good, not amazing, you won't be playing the game for the corruption aspect. If you want to play the Pure Love route, it's worth it.
The story's fairly simple on the "main" Corruption route: you peep on the girl, get blackmail videos, break the girl, get one of 3 endings that are EXTREMELY underwhelming, and can be read in less than a minute.
Gameplay is the classic "Break her with pleasure" gimmick where you do arbitrary stuff that pleases her (or not), and your ending is based on it.
Before the sex part, you need to scout her house, get cameras then install them, and sometimes go to Akihabara to get some specific items to be able to install the cameras.
The H-scenes themselves are alright, the voice acting is often repeated, which makes it really dull after 4-5 scenes, but the VA really did a good job and absolutely carries the scenes. The character models really look outlandish in contrast to the extremely realistic background, but it looks okay.
The settings in the scenes are pretty lewd though, it's fairly generic in the realm of hentai (example: fucking while she's on the phone), but I've rarely seen games doing that, so it's pretty good.
Everything I've reviewed so far is about the Corruption route though, and the opposite is the Pure Love route, and makes the game
truly worth playing.
Instead of peeping on her to get blackmailing material to break her, you'll still peep on her, but rather to get close to her. Her best friend is extremely (and rightly ) suspicious of you, and you'll spend your entire time trying to get close to both of them, and get their approval.
In the proccess, her best friend
To get the route, you'll need to spend a lot of time having short conversations with them, with absolutely 0 repeating events. And there's A LOT of events to go through, which makes going through the route really interesting. Since all the events are linear, you can clearly see both girls warming up to you, starting to rely on you, and there's a great mix of having a slow, gradual build-up while still feeling a degree of constant progression in your relationship.
For a game where they explicitly warn you that the Pure Love route is an afterthought, it felt like the most interesting route to me, and gives the self-insert character a level of depth and complexity that is completely unexistant otherwise by having his love interest be the main motivator to redeem himself. There's no outlandish drama, just two people falling in love with eachother, one of which who used to be massive creep, and that in itself makes the experience worthwhile.