At a Glance: Rosario + Vampire
Yokai Academy is a boarding school for monsters. It's dedicated to helping them pass as human, so the students look human and are not allowed to use their powers during school hours. However, humans found among the students will be killed.
Our generic boy protagonist, Tsukune Aono, finds himself rather by accident to be one such human. At first he wants to leave when he realizes what Yokai Academy really is. But when he kind of falls for Moka, a cute pink-haired vampire girl, he decides to stay and try to keep hiding the fact that he is a mere human. When Moka's rosary is removed, she becomes a silver-haired, very powerful vampire with a different personality.
Basically this becomes a pretty funny ecchi/harem anime, when Tsukune meets a succubus, a witch girl, and an ice-powers girl who all want a piece of him. (Even a murderous mermaid tries to bag him.) So, kind of like in Monster Musume, this dude has a pretty cool harem, but they all have the potential to freaking kill him. He could also be killed for simply being outed as a human. But oh, it's worth it for all the panty shots, right?
Rosario + Vampire
Comedy, Romance, Harem, Supernatural
Manga by Akihisa Ikeda
26 (2 13-episode seasons)
Novel, DS Game, PS2 Game
You'd probably think this show is just comedy and fanservice, and that is a portion of it. But it's also primarily about Tsukune and Moka's relationship, which adds romance. The monster stuff adds action and horror elements. So this show ends up having a really good story for a harem anime. It will get you in the feels, make you laugh, and make you afraid for the main characters' lives.
That being said, the animation isn't that great. It seems slow and often reused. They have a major fight in most episodes (or in all of them, I don't know for sure) and the fight is where they spend their budget, so the things leading up to that point are animated in low frame-rates and with a lot of repeated sequences. So honestly, you're probably better off with the manga, because while I came to like this story and the characters, I don't think the animation is that great. And the manga format is probably better for the fanservice, because manga tends to show more stuff, if you get my drift.