Ichiban Ushiro no Daimaou (aka Demon King Daimo) is an echhi harem about the future demon king and his highschool life.
Akuto Sai dreams of one day become a high priest. Unfortunately he and the rest of the school find out he's destined to be the future demon king.
This ends up getting him all sorts of unwanted attention:
-Hattori Junko a blue haired girl, the first girl he forms a bond with at school hates him now. She provides alot of the fanservice.
-Korone a green haired government android who's job is to survey Akuto. She also provides alot of the fanservice. Arguably the best character. And the best tease.
-Soga Keena the redhead, an airhead who can turn invisible and is often times naked. She also provides alot of fanservice.
-Fujiko Etou, a purple haired girl who wants to rule the demon king. And as you can already guess she also provides fanservice.
-Eiko Teruya with long green hair who likes flirting with Akuto.
Akuto is admired by Miwa Hiroshi, a boy who admires him for being the demon king. But turns out Hiroshi is destined to be the hero.
The characters are all very entertaining. Had me constantly laughing.
At first i felt the show was introducing way too many characters way too quickly. Specifically the female characters. They just showed up so quickly one after the other. But ultimately i ended up liking them all.
Strangely enough for a harem that constantly shoves breasts and panty shots in your face it does take itself very seriously at times.
Episode 7 is where it starts to take a dive. Started taking itself way too seriously and lost its fun tone. It even became a sentai out of nowhere.
12 episodes was not enough to develop some aspects of the plot.