Akutabe, a detective, summons devils to solve the troubles of his clients. One day, a low class devil Azazel Atsushi is summoned by Akutabe and is used harshly by him and his assistant Rinko Sakuma. (From ANN)
It's a dark comedy with strong sexual references, language and violence. Not usual my type of entertainment but it was surprisingly funny.
The sexual theme is there mostly because the demon, Azazel, is a demon that incites lust.
Kugimiya Rie got boned in this episode... I couldn't believe it. You'll have to watch it to understand.
Also there's an OVA of this, it's more hilarious than the TV series so far imo.