A millennium ago, the vampire queen Adelheid nearly destroyed the world for the love of her king, unleashing the dangerous "moonlight of corrosion" which destroyed everything in its path. In the end, she was sealed by the power of vampire, dhampire, and human alike; but her king, Akabara, searches the world for the seal that will release her from her captivity. Humanity at large has since forgotten the existence of vampires, but the dhampires remember, and they will do whatever it takes to kill Akabara before he rescues his beloved queen.Against Akabara is Bridget, powerful ruler of the Dhampires and a group of elite warriors including Jin, whose beloved was killed by Akabara. With them is the Black Swan, a parasitic magic that possesses young women for the sole purpose of killing Akabara and Adelheid. The most recent host is strong enough to kill Akabara, but she instead sides with him, to the shock of the dhampires. It seems things are not as simple as they seem and old enemies may have to unite to survive.The Reveal ensues. Several times. Also Genre Shift and Gambit Pileup.
Bitter Sweet Ending: Strauss and Adelheid are able to destroy the aliens and saved the Earth. But Adelheid sacrifice herself to terraform the moon so the Dhampires can have a home of their own. Strauss and Kayuki finally have their duel where she finally kills him, ending the Curse of the Black Swan that's been slowly killing her and freeing Strauss's wife and daughter souls and freeing Strauss long life torment where he can finally be reunited with his family in the afterlife and leave the world to his friends, allies and adopted daughters.
Book Ends: The manga begins and ends with Akabara fighting against the black swan with the difference being the end result.
Broken Aesop: One of the morals seems to be that there is no such thing as complete evil and that everyone does something for an understandable reason, yet the reasoning behind the aliens' actions is never explored leaving them as simply evil.
Chekhov's Gun: When they first meet, Akabara tells Letty a story about the origins of vampires. He also tells her that he could fly to the moon. This turns out to be more important than you might expect.
Combat Pragmatist: "Infinite Cross" Saberhagen, who was willing to kill her own adopted daughter and grandchild to create the Black Swan curse that could eventually kill Akabara.
While he is often Willfully Weak, Akabara, when given the opportunity, does not hesitate to demonstrate why he is the greatest tactician and strategist to ever walk the planet.
Cool Mask: GM, or Great Mask, who effectively controls the country and his granddaughter Kaiyuki the 50th Black Swan when she's introduced (she's shy).
Disproportionate Retribution: Akabara is without question the absolute nicest guy in the entire series. But just because he just happens to be the most powerful thing to ever walk the planet, he is ultimately sentenced to being hunted down by the Black Swan, which is a curse created from the souls of his beloved wife, Stella and his unborn daughter, that will reincarnate over and over again until he and Adelheid are dead. Sheesh!
Expy: GM is very reminiscent of Kiyotaka from Shirodaira's previous series, Spiral... just replace the mask with a furry costume and add more quirks.
Fate Worse Than Death: Jin, whose would-be girlfriend, the 49th Black Swan, has been suffering quite a bit after she is killed by Akabara. Ultimately, he finds out that he has nothing on Akabara himself who has spent the last thousand or so years deliberately acting the part of the villain in order to earn the hatred of both humans and dhampires and unite them against him so that they don't start killing each other. And to make matters even worse, on a regular basis he ends up fighting and killing young women possessed by the souls of his murdered wife and child... over and over again.
Flashback: There are a lot of these to a thousand years ago, each revealing more to the audiences and in several cases, completely changing the meaning of the events in the manga.
Generation Xerox: Many of the previous Black Swans resemble Akabara's wife Stella due to her soul being part of the spell.
It was hinted some of the Black Swan hosts might have been how their unborn child would have looked like, which Strauss citing Yuki, the 49th Black Swan, as the best example of what he thought their unborn child would have been like.
Gentle Giant: One member of the Dhampyr's Akabara killing squad is a giant man in samurai armor who also runs a tiny (but highly-recommended) noodle shop as a hobby.
Heroic Sacrifice: Akabara wants peace so much that he's willing to take on the hate of humans and dhampyrs onto himself and Adelheid wants to make up for not preventing Stella's death, so they're both going to fight the Big Moura.
Adelheid sacrifices herself to terraform the moon.
Our Vampires Are Different: Specifically, they are organisms from space who, during their evolution, took on enough of humans' genetic information to resemble them and reproduce with them but are still a different species. The need for blood was eventually bred out too.
Akabara is even different from other vampires: He can move in daylight and fly to the moon. Unexpectedly, Adelheid turns out to be even more powerful than Akabara.
Sweet Tooth: Akabara loves cake (and ice cream and Pocky and parfait and...).
Sword of Damocles: The aliens act as these encouraging the factions to work together although there are still plenty of gambits going on although there were partially aware of this and took some token measures to defy the trope. Akabara also acted as one of these for the past 100 years letting himself be known as an all powerful enemy to both dhampirs and humans in order to unite them.
Xanatos Roulette: All the events in the story after the great disaster except maybe the alien invasion could easily have been planned by Strauss.
Zero Approval Gambit: He's actually trying to get both sides to unite in hating him, and if they kill him all the better. He acknowledges that if Stella hadn't died he may have been able to figure out a better plan.
You Gotta Have Blue Hair: Strangely enough, the only character with odd haircolors are Strauss (blue) and Stella and two of the Black Swans (pink) and that similarity is not a coincidence.