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A Catholic priest who seems to be nothing more than a clumsy, absent-minded fool on the surface. In truth, he is a Crusnik, a vampire of extreme, extraordinary power, and is an ancient being, hundreds of years old. He is a vampire that feeds on the blood of vampires. But despite his strength, he adheres to a principle of pacifism and often refuses to outright kill his opponents. Abel is shown in flashbacks to have a hatred for humanity, but at some point that changes into his current pacifistic and peaceful outlook on life. He acknowledges having greatly sinned at some point in his life, though it is unclear as to what sin he committed, and much of his current personality is based on retribution for his sins. Abel has at one point referred to his Crusnik form as "a mark of his sins", though it is unknown what he meant by that. He has feelings towards Esther Blanchett, though they are more related to her similarities with a woman from his past. In his human form he fights with a gun that shoots silver bullets. As a Crusnik, is able to transform into various forms based on the amount of nanomachines in his body that he activates. In his higher forms he wields a huge scythe materialized from his own blood. In The Star Of Sorrow II, it is revealed that pre-Armageddon, Nightroad was Commander in the UN Air and Space Force involved in the "Red Mars" project.

Abel was created in 2088 A.D. in London as one of the so-called "Test Tube Babies." There four artificial humans (Lilith Sahl, Cain Nightroad, Abel Nightroad, Seth Nightroad) were created to be in charge of the colonization of Mars after the Earth's population drastically increased. On Mars, the colonists discovered two alien technologies (the Bacillus and the Crusnik nanomachines), which they installed in their bodies: the colonists, the Bacillus; the Test Tube Babies, the Crusnik, since only their enhanced bodies were able to survive this combination. As the colonists returned to Earth, a war broke out between them and the humans who remained. Abel (hating the world for creating him and his beloved "siblings" as toys back then), Cain, and Seth took the Methuselah's side — while Lilith supported the humans' side. After she was killed by Cain (now insane after he had fused with the Crusnik nanomachines at 100%), Abel retrieved her body, and, in grief, brought it to the Vatican, where she was buried. For 900 years, Abel stayed by her side and wept, until young Caterina Sforza fled to the crypt as she was chased by Methuselah assassins. Abel, realizing that it was his task to continue Lilith's work and defend the humans, saved the young Caterina and chose to live on. He joined the AX at its foundation in May, 3055 A.D. Also, in "The Night Lords V.", Abel finds out that Cain is still alive. Near the end of the series, Abel is apparently killed by Cain. Father Tres later gives him Lilith's nanomachines, reviving him in 100% Crusnik form. Cain and Abel fight, but neither of them is victorious. During the ending credits, it is shown that Abel is indeed alive and is joined by Ion in his quest to kill Cain.

At the start of the series, Saya appears to be a high school girl living a normal life on the Japanese island of Okinawa. She is adopted and has no memory of her earlier than one year ago. She is able to heal all her injuries very quickly but must regularly receive blood transfusions or drink blood to remain healthy.

Despite these strange traits, she has the outward appearance of a young human teenage girl with an unusually large appetite (used as a humorous effect several times), most likely a side effect of her inhuman metabolism. However, she does start having more flashbacks of her experiences fighting Chiroptera in the Vietnam War and in 1920's Russia. Her oldest memories are from her birthplace at Joel's mansion called the Zoo in 19th century France. She was "born" in 1833 from a cocoon like object taken from a mummy of a Chiropteran along with another cocoon containing her sister Diva. She also can spend decades hibernating in a cocoon, only awaking for a few years before sleeping again. Whenever her and Diva's blood mix, the blood crystallizes and disintegrates. She is a skilled athlete and her weapon of choice is a nihontō (Japanese sword or katana) with bohi or grooves specially designed to spread her blood through its entire blade, making it a deadly weapon both for Diva and any Chiroptera made from Diva's blood. The first blade in the series is broken by Amshel, but she acquires a new sword from David with a red crystal at the base of its blade. This crystal is actually a piece of her adoptive father George's blood which crystallized when she killed him with her own blood in order to spare him the fate of fully becoming a Chiropteran.

Saya's human personality is usually that of a cheerful and optimistic girl but her suppressed vampire side (evidenced whenever her eyes turn red in contrast to her twin sister Diva's blue eyes) is infinitely more cold, calculating, and with a warrior's edge that brooks no foolishness. However, as of late Saya has had very little to be cheerful or optimistic about as she learns more and more about herself and the enemies that stalk her. Her greatest fear is perhaps finding out that she is indeed the same or much worse than the very monsters she now hunts as hinted by the grisly yet splintered memories she has of her dark, shadowy past. It is revealed that after she and Hagi had left the 'Zoo', she made him promise to kill her after Saya has slain Diva so as to prevent the survival of the Chiroptera. Post episode 33, Saya gains a much darker appearance and personality, sporting a dark maroon trenchcoat and generally longer hair.

Past this point in the series, her willingness to co-operate with the Red Shield and with her own family drops, as she wishes not to endanger them any further, believing that her fight with Diva is hers to fight alone. This somewhat marked change in Saya's normally cheerful personality is also accompanied by an acceptance of her Chiropteran biology, with a willingness (of necessity) to feed off of Hagi's blood with little shame.

Saya confronted her sister in the Metropoilitan Opera House, and the duel ended with the sisters piercing their swords through each other. Though Diva began crystallizing, Saya survived as Diva's blood lost her potency due to her having children. At Kai's pleas, Saya made a decision to live instead of die and to also let Diva's twins live. Shortly after her return to Okinawa, she went into her hibernation period, and Kai along with the twins watches over her as she rests in the Miyagusuku family grave. Hagi also visited, leaving his hair ribbon tied around a rose.