The pitch is you play as a green haired "yokai", which is a type of spirit in Japanese folklore whose personalities can range from malicious to benevolent and friendly towards humans. Yuka is minding her own business when an old man trespasses on her property with intent to make her his sex slave. She intends to kill him for trespass, but he came prepared, and activates a charm that pulls the both of them into a pocket dimension. There she finds her super powers are all neutralized, and she has to solve the mystery of the pocket dimension, gather four key-balls and open the door that'll get themback to the real world.
Along the way, she gets sexually harassed by the old man, and the dimension itself periodically fills with increasingly humid air and aphrodisiac gasses, making Yuka horny and sweaty. As you finish events, you hit milestones where you can enter states of greater undress (culminating in walking around naked), and repeat each event with Yuka being more eager and horny. You can complete the game before she's completely worn down by her captive state, which is a nice little option.
Overall it's is a nice compact little puzzle adventure, with very light point-and-click mechanics like "find a knife and whestone, use the whetstone, the knife becomes sharp enough to cut a curtain, which accesses a switch, which opens a door, which..." and so on and so forth. The puzzles are very logical and really breadcrumb themselves, plus there's a hint system and a switch that will point out places you can click with giant green arrows.
The best part of this game is the level of smut content matches the size of the game. There's no grinding, there's no needlessly expansive world map, there's no repeating content over and over until you hit an arbitrary number value. The adult content itself is typical of most Hentai Games. A still image is displayed and a few boxes of text imply what's going on. It's very limited, and where most games falter is they don't think the rest of the game should be equally limited to match this restricted format.
As for the specifics, the protagonist's body is outrageously proportioned, more than I'd like, but the art is good. I wish the old man had a tiny bit more detail put into him, since he's the only other character. Usually in these kind of games, the old perverts get generic art because it's recycled over and over. That wasn't necessary here, since it's just the one.
Overall, this is a good little diversion, which doesn't outstay its welcome, which is a major design issue with the whole 2D CGI hentai genre. Short, to the point, and knows what it is.