Idol Kouhosei is a 19 minute hentai (with currently only one episode) that consists of three 5 minute sex scenes. They also have pointless minute-long credits in the middle of them and re-introduce the "plot" with each arc. The "plot" is basically that, due to the low population of Earth, a project to create idols who can apparently sing and dance but most importantly (and the only thing shown) have sex. Each arc is pretty simple. The girl shows up at the hardly-ever-shown guy's door, comes in, and has sex with him. Also, all three girls are still virgins who have just become idols. As forthe three arcs, they vary a lot in how good they are:

1. Cool, tan girl who meets the guy for the first time. 8/10
2. Wimpy sounding, blue haired childhood friend of the guy. The guy is more aggressive in this one than the others. 3/10
3. Loli childhood friend of the guy who calls him "onii-chan" despite not being related (I have no idea what kind of government sanctioned project allows 12-year-olds to do this kind of stuff but whatever). 6/10

The art in the first sex scene is great, slacks in the second scene, and recovers a little in the third. The girl's voice in the second scene is very annoying, but both of the other girls' voices are fine.

I enjoyed this hentai a lot except for the second sex scene. It's a pretty simple vanilla harem hentai and if you don't like loli girls at all you could just skip the last scene entirely.