It's kinda difficulty to outright find a hentai (despite the fact that this series claims it's an echhi series, it has full blown explicit sex, so I'm probably going to call it a hentai anyway) that's just fun to some degree. Sure, most hentai is supposed to be fun since it's trying to cater to someones fetish first and foremost, but it's not that often that the stuff around that sex is meant to be just as entertaining. That's where "Joshiochi!: 2-kai kara Onnanoko ga... Futtekita!?" (Eng: A Girl Comes... Falling from the Second Floor?!) comes in.
Out extremely basic ploy follows Sousuke, a self-proclaimed bum who would rather work part-time than go to college. Because of this poor life decision, he's pretty poor, and has to live in a rundown apartment building where the only thing he has worth looking forward to in his day-to-day life is the cute landlord. He soon finds out from a noise from upstairs that the person living above him is another cute woman.
Before he knows it, the woman who lives upstairs floor breaks, with her crashing through and landing right on his dick, resulting in them fucking right then and there. The rest of it is a series of events that leads to him fucking both the landlord and the upstairs tenant.
The episodes are only roughly 4 minutes long each, which means that the sex scenes aren't all that long either. But weirdly enough, this isn't really a hentai in the truest sense. Well, yes, there's full penetrative sex, and there is definitely someone out there who is going to or already have beaten their meat to this, but the whole tone of the show is slightly more slapstick than it is outright erotic.
Thankfully, this series has Satoshi "King of Breasts" Urushihara, a man who is so well know for his breast physics in anime that every 2D boob he's ever drawn is the cream of the crop and is going to be worth checking out. As as expected the animation and art is top notch, despite that a few scenes are not as animated as I'd like.
If you just want something to wank to, this is not half-bad, but there is stuff out there where the sex scenes actually last a decent amount of time. I'd highly recommend this to someone who likes a bit of comedy in their hentai. Also, depending on which fan subs you go with, those can add a bit of fun to the whole thing.