The previous reviews are a little misleading. If you read the author's note at the end, they say that originally Kei was a vampire but they realized they hadn't drawn Kei sucking blood at all. So that gives background to Kei's story in the sense that's he was originally vampire and therefore no other information on him being a non-human was really needed. The story itself was rather simple and quick paced - renting it is a better choice than buying it.