Vampires as love interests in harem or harem-like anime series are not terribly unusual, but an unwritten rule seems to exist which prevents them from being the central character in such series; when vampires are the leads in anime, either no romance is explicitly involved, romantic options are limited, or (in one case) the central character's vampire status isn't revealed until late in the franchise. As natural as a powerful vampire having a harem may seem - they are sometimes depicted in movies and literature as having a bevy of beauties at their beck and call, after all – their absence in these cases is presumably because being a vampire implies a degree of confidence and bravado that makes for a good love interest but does not fit well as an audience-insert harem/reverse harem lead. Original light novel writer Gakuto Mikumo, whose other major works include the source novels for Asura Cryin' and The Mystic Archives of Dantalian, found a way around that: make the male harem lead a fledgling vampire (albeit a very powerful one) who is still figuring out the ways of being a vampire.

That gimmick constitutes almost the entirety of the true originality in this 24 episode series, whose broadcast spanned the Fall 2013 and Winter 2014 seasons. Otherwise the content is par for the course for action-oriented harem series based on light novels: a succession of 2-4 episode story arcs which forms continuous narrative and character development (if not necessarily continuous plot) and involves an eclectic mix of super-powered (in this case magical) and technological elements. As the protagonist progresses through a series of dangerous situations, one female character primarily remains by his side but numerous others gradually gather in orbit around him while male characters are kept to a minimum. Some room is left for romance, but not too much. The situations the core cast members find themselves in give both the lead and various side characters chances to show off their powers/abilities. Naturally the protagonist occupies one of the lowest levels of the environment's power structure, so many manipulations are going on which lie vastly above his head and beyond his comprehension and he can only muddle through as best he can.

If this all sounds a lot like oh, say, A Certain Magical Index, that's because the series seems to have at least subconsciously modeled itself off of that franchise. The circumstances, character backgrounds, and plot lines may be entirely different, but the way events progress, the way the action scenes are staged, the balance of humor and more serious events, and the general structure of the series give it a very similar vibe. It even has some duplicated concepts, too, such as most events taking place in a city made special by the prominent presence of supernatural elements, characters from an outside magical organization infiltrating the city, a secret program which forces super-powered youths into deadly battles to create stronger warriors, and an adult teacher with the body of a child (although in this case why she is that way is actually a major plot point in one arc rather than just a gimmick).

While the vampire element comes into play on a regular basis, it is more a complement than a focal point, an excuse for Kojo to be super-powered and draw so much attention rather than an in-depth examination of vampire nature. Never explained in the series is exactly how Kojo ended up as a vampire; it is alluded to on a couple of occasions, but the pieces do not add up well. (It is apparently explained much more thoroughly in the novels, so perhaps an OVA episode will pop up at some point to detail it.) Connecting the harnessing of Kojo's vampire powers to his libido is an amusing variation, but again, not out of line given the erotic component which is so commonly an undertone of vampire bloodsucking. However, that and the way that the Lion King Organization handles Yukina over the course of the series does raise the intriguing notion that perhaps a nubile girl being specifically chosen to be Kojo's observer might not be just common anime gimmickry; it may instead be a carefully-calculated ploy to influence Kojo in certain directions. An occasional bite does, of course, result, and the eroticism of those moments is handled effectively without being overplayed.

The character types and personalities in play are fairly standard, with Yukina being a typical mild tsundere type; she gives Kojo a little more understanding than normal in situations of inadvertent voyeurism/groping or being caught in compromising positions not of his own doing, but not by much, and nothing is unusual about the way her distrust of him gradually grows into affection and teamwork over the course of the series. Her chief romantic rival, Asagi, is also typical as the “female friend who secretly pines to be more,” although she is not the “female childhood friend,” too; that character pops up separately later. She is unaware of Kojo's nature, and so the series has to be careful to keep her in the dark, but she is a computer whiz with a significant role in supporting the island's well-being. (The extent of her computer ability is occasionally vaguely implied to be supernatural, though the anime is never clear about this point.) Sayaka, a friend and work comrade of Yukina's, also comes into the picture early and lingers throughout the series, and of course she eventually becomes attracted to Kojo, too, even though she is initially implied to be more interested in Yukina. A bevy of other beauties pop up over time, including two girls who are strongly implied to be the future progeny of major series characters. Only two other male characters recur throughout the series: a friend of Kojo's who (naturally!) is involved in clandestine activities himself and a scion of one of the other Progenitors, who initially comes across as a villain but instead proves to be a thrill-seeker who is interested in Kojo because he loved Kojo's predecessor as the Fourth Progenitor. Again, all pretty typical stuff for series like this. The only actual new character is Mogwai, Asagi's virtual partner, who is initially implied to be an AI Asagi created, but later scenes suggest that he is his own person with his own motives which just happen to dovetail nicely with Asagi's activities.

While nothing about the characters or the story arcs stands out, the series does deliver quite well on the action front and does excel in one important aspect: it has an exceptionally appealing array of female character designs to surround Kojo with. Keiichi Sano, whose other prominent character design effort was Heaven's Memo Pad, strikes gold here with designs that range from merely pretty to absolutely gorgeous, and the overall artistic effort gives them loads of sex appeal without resorting to more than occasional scenes of implied nudity, unusually high-quality lingerie shots, and manufactured excuses to put female characters in maid and nurse outfits; in other words, fan service is generally used more as an enhancement here than a point of emphasis. Otherwise the artistic and animation efforts by J.C. Staff are solid but not exceptional for most of the series, with a significant downgrade in quality control over the final few episodes and in random spots before that. Graphic violence is significant in places but nothing that would earn the series more than a TV-14 rating.

Opening and closing themes are another place where the Index franchise comparisons can be drawn, as the intense synth-based sound used in them heavily resembles the style commonly-used in the Index franchise and one each of the two openers and closers feature a performer who also sang for an Index title; in fact, the voice of Index, Yuka Iguchi, is the singer for the first closer. Both openers have a similar rock-edged, upbeat feel which suits the series well, while the second closer is a softer and more melancholic piece than the first one; in each case, the new one takes over with episode 14. The numbers used in the main episode content serve quite effectively at enhancing both dramatic and more light-hearted aspects. Japanese voice work, contrarily, is entirely unremarkable.

Despite its lack of freshness, Strike the Blood executes well enough, and establishes a convincing enough relationship between Kojo and Yukina, that it still proves plenty entertaining. It may be built on a tried-and-true formula which has developed over the past few years, but it does not mess it up by striving for anything too grand, by deigning to inflict preachy ramblings on its audience (see Index), or by generally failing to make sense (see Asura Cryin'). Its final episode wraps up its current plotline but does throw out plenty of potential hooks for an eventual continuation. No such indication was given at the end of the final episode, but this one not getting some kind of additional animation at some point would be a big surprise.