- Awesome Music: The anime opening, "Scarlet" by Brace;d.
- Broken Base: The manga ending, with Karin's family erasing her memory of them and of vampires to let her live as a human with Kenta. A nice Bittersweet Ending fitting the tone of the series or gratuitous drama that unnecessarily spoils a happy ending? Opinions are divided.
- Esoteric Happy Ending: Again in the manga. Yeah, Karin and Kenta have their happy ending, but, the vampires will likely become extinct because all of the women, sans Calera, are infertile. Then again, Ren has a son by Bridget... Although, while not outright stated, it is implied that the Psyche being released from her physical bonds has released vampires from the curse of infertility, allowing them all to rebuild their population.
- Heartwarming Moments:
- During a flashback, when Elda is struck by a craving for blood due to not feeding for a while, she tackles Alfred to the ground. Even with her snarling down at him with glowing red eyes and sharp, pointy fangs, Alfred is taken off guard for all of three seconds. Then he relaxes and tilts his head to better expose his neck for her. D'awww...
- Ren practically going on a rampage when he finds out Karin had been kidnapped.
- Ho Yay:
- A good part of Episode 18. Ren thought that his classmate, a Bishōnen boy, was a girl. However, he realizes toward the end what the thrumping in his chest is: he discovered his blood's anfinity. So he naturally grabs the boy and sinks his teeth into his neck. The reaction from three male students is pretty similar to a Yaoi Fan's.
- Memetic Mutation: OH MY GAHHH! NOOOOOOOOOOOOOOOOOO!!!
- Narm: Pretty much the entirety of the English dub of the anime;, to the point where it's downright unwatchable for some viewers.
- Nightmare Fuel:
- Boogie, an already creepy-looking doll with a knife attached to his hand (holy shit!), can turn into a sanity-destroying monstrosity. With a knife. Yeah, dolls are scary.
- Berserk!Karin, when she holds her blood in too long. It's shown that any vampire who does not bite a human on a regular basis has a tendency to slip into it, but seeing adorable little Karin reduced to primal fury is its own kind of scary.
- The Van Helsing Hate Crimes are shown in full during Elda's flashback. We get a harrowing scene of a vampire family executed under the sunlight: a husband, wife and son who we get to see slowly and agonizingly desiccate under the sun until they're nothing but shriveled charcoal. Considering this is a romantic comedy, it's not what anyone expected to see.
- Unintentionally Unsympathetic: Both Karin and Kenta can fall on this due to their strange compunctions about her vampirism. Kenta, for one thing, acts offended when Karin's instinctive bite paliates his mother's depression and makes her strong-willed enough to fight off her harassers, and even claims he wants her back to her previous state! Even worse, Karin somehow agrees him and refuses to do it again. This is part of the same problem, as Karin also refuses to bite Kenta even when it would be harmless for him (she doesn't even suck blood, she gives it) and would make him happy enough to end her blood ordeals.
- What Do You Mean, It's for Kids?: The manga is shonen despite having a fair amount of blood and sexuality, and it doesn't help that its creator has drawn hentai and eroge games. However, given the heavy parallelisms drawn between Karin's condition and the human period, it's probable the author had in mind precisely to help young female readers to get comfortable with their sexual maturity ("geez, at least my monthly problem isn't spectacularly visible like Karin-chan's, I guess it's not so embarrassing after all").
- The Woobie:
- Karin is the black sheep of the family because of her ability to give blood, stay in the sunlight, and eat human food, and thus, she is one of the loneliest vampires. When her little sister Anju becomes a full vampire, she realizes how alone she is and she cries as she makes breakfast for herself.
- Also, in the manga, you can't say you don't feel sorry for her when memories of her family are erased and she thinks of them to be dead after graduation.
- Iron Woobie: Elda. She could have had what Karin had, and it's clear that even now she dearly misses Alfred. Unfortunately prejudice against vampires was at full swing at the time, and her affinity (love) was the final nail in the coffin for their relationship.
- Yuriya Tachibana, who is a half-vampire, half-human hybrid. After her father died, her mother struggled to raise her alone, and passed away from the stress. Her first biting victim was someone she loved back in junior high, and, as a result, she was forced to leave town. She is ostracized by the rest of the vampires because a "half-breed" outed the existence of vampires to a human church a hundred years ago, and they were nearly wiped out, and they see her as a threat. Elda almost killed her until Karin intervened, and Bridget is especially nasty to her, calling her an "empty doll" and suggested that Yuriya kill herself, but hasn't yet because she doesn't have the courage to do so. Her Uncle is the only person she can rely on.
YMMV / Karin