So let's start with episode 1,
in the first scene the male protagonist Yuuto is sleeping and a pink haired girl comes into his room. She says she's a vampire but looks more like a Succubus with the bat wings, the arrow demon tail and the ability to grant wishes. She says that she's gonna suck his soul...so yeah she's a Succubus.
But the series is actually getting ahead of itself so lets see how it all started:
so the boy was hired to be the servant at this mansion where lives an oldish man and 3 hot women (a blond, a green haired and a pink haired
one) with huge breast and who dont wear bras.
The boy is replacing his father who the old man claims to be a criminal (maybe that will be explained in ep 2)
Now lets go back to the boy and the Pink Haired. He's supposed to die by tomorrow since his soul was sucked (actually his dick was sucked, his soul was sucked through his dick, seems like a good way to die)
Tomorrow comes and he's still alive! Could he be "The One"?!
We'll find out next episode.
So yeah he's the chosen one, not much to tell. He does end up evolving from Yuuto to Super Yuuto though, he ends up looking like Inuyasha and Demon Kurama (from YuYuHakusho).
There are two (and only two) vampires - the two sisters (Serena and Marie). Yuuto was, in fact, raised as a human (despite his actually being the son of the king) - even he himself is not aware of that. Other than Marie and Serena, Mizuki is a demon (but not a vampire), and is the household maid, Sister (the one dressed as a sexy abbess) works at the school (where Yuuto, Serena, and Marie are all students); however, she is human. The old man is the father of the vampire girls and has doubts about Yuuto - in fact, he thinks Yuuto
is the son of a traitor to the family - his doubts don't go away until his face is - literally - covered in egg and he HAS to deal. Mizuki doesn't find out that Yuuto is the prince until everyone else does (even though she is - literally - the first to jump him back in part one); the Sister also has no clue (despite HER jumping him at the beginning of part two). Serena is upset because she lost HER chance at jumping him (first to Mizuki, which she is not aware of, then to the Sister- which she IS aware of) - a major case of "jealousy" - not anything else. As to *why* Yuuto chooses "from behind" with the maid, Sister, and even Marie, two words come immediately to mind - "Treasure Chest"; all three are blessed with one; he has no desire to squish the "pillows" with his body. (I have the same weakness in real life - and I'm not Japanese.) Still, I have to wonder three things.
1. Will Mizuki go back to the demon realm? (She mentioned going back after she drew her sword on the old man to protect Yuuto.)
2. Regardless of whether she goes back or not, will she 'fess up to boinking Yuuto (which is why Serena didn't get HER chance until later)?
3. Will Sister get another shot at Yuuto? (Sister was in the room with everyone else when Yuuto's secret was exposed - so she now knows that Yuuto is the king.)