Open Flower is a VN about a married working woman and the sexual hoops her new job forces her through. Just to send off the people who aren't okay with it, the ntr is absolutely unavoidable.
The game has a lot of good ideas with its scenes as long as you're into hard ntr. Unfortunately, the execution can be more than a little lacking. The grammar and word choice is frequently rough. While it's nowhere near MTL levels of word salad, a lot of scenes and conversations are understandable, but extremely awkward. Also, I have no idea what's up with the random Japanese flashcards either.
There's also a handful of scenes with positively awful lighting. I rarely complain about things like this but there several sequences in the game where all you can really see is a mess of greys and blacks. It's not meant to be some kind of ntr edging, there's just extremely dim light that ruins some scenes.
The actual gameplay portion of the game lacks pretty aggressively hard. You play as the female lead's useless husband, as in many ntr games. The story is told through snapshots related to you by your wife as you ask her about her day. There are options available to encourage her to share more and to encourage her to be more slutty.
While there's a general sense of what each response is aiming for, it's basically only trial and error that will allow you to see all the scenes. A lot of this is due to the language problems, but it's also because it's difficult to tell which response might skip a scene or not. There's also a number of scenes that repeat throughout the story, which is annoying since you can't even skip them.
In addition, the game can't seem to decide what kind of relationship the two main characters have. In some scenes the wife is dismissive of the MC, treating him like a useless annoyance. In other scenes, they have a good relationship with the MC supporting her hotwifing. The dichotomy between the two changes at the drop of a hat. As near as I can tell, your decisions throughout the game don't appear to change this.
All in all, I wish I liked the game more. It has a lot of good ideas for hot scenes, but the actual game tying them all together is very low quality. I can only recommend this game if you're really into ntr, you really enjoy the screenshots, and you have some time you don't mind utterly wasting.