This is definitely the best Hentai I've watched, and the combination of a romantic drama with full-on sexual scenes makes it one of the most interesting animes I've watched. It's a romantic erotic drama and the leads are two high schoolers in love. It's all about their mutual love and attraction, you don't get to experience fear, depression or unease as the usual case with Hentai. The show has a more-than-usual focus on drama, even the sex scenes exists with character or story development intentions. Another thing special I found here was how much the show supported monogamous relationships and there's almost no sexual relations other than betweenthe two leads.
To me, it felt like the much desired "Hentai for girls", in the sense that the girl has a big role in the story and the situations are mostly there for her pleasure.
I would also say that the art, characters and jokes reminded me of shoujo shows more than shounen - mainly Fushigi Yuugi and Puchi Puri Yuushi.
Highly Recommended.