And then of course, there is sexual fanservice, occasional steps into "ecchi" or "hentai" which happen in series which are, in itself, not really about sex. As you can imagine, these definitions are not exactly strict, leading to quite some blurred areas (pun not intended).
Prison School is a series which defies easy pegging, though for safety's sake I'd label it "ecchi". In it, five students are the first boys to be allowed to join a prestigious boarding school for girls, but after being caught peeking in the girls' shower area, they get a choice: be expelled or be sent to a special prison wing, where for one month they will be the masochistic playthings of several sadistic female wardens. The boys all choose the prison wing and things get very weird after that.
Like Kill La Kill, Prison School relentlessly spoofs fanservice, "ecchi" and "hentai" while providing lots of it as well. It's satire by way of exaggeration, and while it walks a sleazy path, it constantly asks you "Is THIS what you wanted?" and, should the answer be a yes, "WHY THE HELL is this what you wanted?"
Anime Limited released the series on Blu-ray in the UK last week, and I couldn't help but laugh when I saw what the cheeky distributor from Scotland had done with it. So here is a gallery of shots. Click on the edge of the pictures to scroll through them, or at the center of each to see a bigger version!