I imagine tags, pics and description can be very confusing as to what is this game? Is this NTR? Is this voyeur game? Do we have some action with Yuuka? Well, let me describe it shortly:
Yuuka got into problems and had fragments of her common sense thrown all over the land. You're... a guy, who was around and could see her fragments, while she couldn't, so she forces you to go with her and search for it. You go around and collect it, doing some mini-quests on the way, and that's all. You don't get to have anything to do with Yuuka, she doesn't dominate you, you have no romantic relationships, you don't even get to look at her having sex(YOU will see it, protag will not), only a few times at her being somewhat naked. Yuuka and protagonist are nobody to each other.
Now, while you're doing that, you can shatter her fragments - and she becomes less resistant to any sexual advances by random guys. By everyone except you, that is. The more you shatter, the more openly she lets them do what they want.
I thought it might be a voyeur game, but protag explicitly says he can't see anything at the rare opportunities he had to watch her. She does it secretly from him, he has no clue what she does. Is this NTR, in the end? Yes, i'd say this is an NTR game, just weird. Get cucked by doing everything while she only lets other men have her. In the ending she still doesn't care about protag, and he started to like adventuring, simply going without her, not really caring either. 4 stars, art is great and gameplay is not that tedious, good as an excuse for scenes with Yuuka.
Additional word: about fights - there's no default rpg maker turn-based combat, you press z and you swing a sword on the map, you damage enemies, they die. Simple, no equipment, only health and movement. If you die you die, there's no scene or anything. 6 short zones and you're done.