Mikaela Hyakuya, the character often referred to as Mickael, is a central figure in the Battle in Nagoya arc of Seraph of the End. He was born to a Japanese mother and a Russian father, suffered abuse from his parents, and was abandoned before being taken in by the Hyakuya Orphanage. There he became the protective older brother figure for the other children, including the protagonist Yuichiro Hyakuya. When a global virus wiped out most humans over thirteen, the orphans were captured by vampires and taken to the underground city of Sanguinem. Mikaela demonstrated cunning by allowing the vampire noble Ferid Bathory to drink his blood in exchange for food and a map, intending to escape with his family. The escape attempt ended in a massacre, and Mikaela was mortally wounded. To save his life, the Third Progenitor Krul Tepes forcibly turned him into a vampire, an existence he came to despise.

Within the Battle in Nagoya arc, Mikaela is driven by a singular motivation: to retrieve Yuichiro from the humans he believes are exploiting him. He views both the human army and the vampire aristocracy as corrupt, trusting only Yuichiro. Despite his vampire nature, he refuses to drink human blood for as long as possible, resulting in severe physical weakness and a struggle against bloodlust. His personality remains kind and optimistic in relation to his found family, but he is also strategic and cautious, often planning several steps ahead. He maintains a complex relationship with Krul Tepes, who saved his life but also uses him for her own agenda, and a mocking, antagonistic dynamic with Ferid Bathory, who orchestrated the orphanage massacre.

Mikaela’s role in the Nagoya campaign is that of a tragic outsider trying to rescue his best friend while caught between two warring factions. He wields a sword that, when commanded to drink his blood, sprouts thorny vines that pierce his hand and turn the blade red; his strength and speed increase in proportion to the amount of blood the sword consumes. As a vampire, he possesses enhanced strength, speed, regenerative capabilities, and the ability to reattach limbs. A weapon containing a powerful demon is required to halt his regeneration. He is the only vampire shown to retain blue eyes instead of the usual red, and he is dependent on Krul’s blood, which becomes increasingly ineffective at quenching his thirst. If starved too long, he risks losing control and attacking even Krul or a nearby human, with the danger of becoming a demon.

The culminating moment of his arc in this season occurs when he finally reunites with Yuichiro. After being mortally wounded, he is forced to drink Yuichiro’s blood with Yuichiro’s consent, completing his transformation into a full vampire and giving him a reason to continue living. He becomes an unofficial member of the Shinoa Squad following the Nagoya battle. Through the events of the arc, Mikaela evolves from a despairing, self-hating being into someone willing to accept a new family while still grieving his lost one. His development highlights the difficulty of preserving humanity when one’s body has become monstrous, and his unwavering loyalty to Yuichiro serves as the emotional core of the narrative.