Yuliy Jirov, also known as Yuriychka, hails from Dogville, a Russian village near Moscow. Born to human mother Sachi and Sirius father Alexei, he is a half-human, half-Sirius werewolf. His childhood ended when vampires destroyed Dogville, killing his family; he escaped only with his older brother Mikhail. Surviving this attack forged his core drive: vengeance against all vampires. Archaeologist Willard rescued him, later founding the vampire-hunting Jaegers under the guise of the "V Shipping Company." Yuliy joined, committing fully to their mission while hiding his werewolf nature from most members.

He possesses a tall, teenage build, deep blue eyes, and long, messy dark blue hair usually tied in a low ponytail, featuring a distinctive white streak near the left side. Activating his werewolf abilities makes his eyes and veins glow bright blue and sharpens his canines. His typical attire includes a pale blue fur-lined coat, a light blue long-sleeved shirt, dark blue jeans, black boots, a bright blue scarf, and an olive green jacket tied around his waist.

Shaped by trauma, Yuliy was initially solitary and unapproachable. He exhibits a strong-minded, vengeful personality, especially against vampires. Yet, he shows deep kindness and protectiveness, particularly towards the vulnerable. He formed a close bond with Saki Hanada, the young daughter of a doctor who treated him, revealing a softer side by reading to her and becoming unusually talkative. He demonstrates unwavering loyalty to his allies, especially the Jaegers, whom he eventually considers family. His sense of justice compels him to oppose unnecessary sacrifice, driving his resolve to reseal the Ark of Sirius without further loss after learning the truth about his father.

Key relationships define his path. His brother Mikhail, turned vampire during the village attack, becomes a conflicted adversary serving vampire king Yevgraf. Trust and mentorship marked his bond with Willard, but it shattered upon discovering Willard orchestrated the Dogville attack to pursue the Ark and rescued Yuliy primarily to use him as a weapon. Despite this betrayal, Yuliy eventually reconciled with Willard upon recognizing his remorse. Other connections include Ryouko Naoe, who developed romantic feelings he largely didn't notice, and Bishop, a former Jaeger turned vampire whom Yuliy trusted regardless, renewing their partnership against common foes.

As a half-Sirius werewolf, Yuliy wields enhanced strength, agility, endurance, pain tolerance, and an acute sense of smell capable of detecting vampire blood. Intense rage triggers his "Beast Blood" state, amplifying these traits but rendering him uncontrollable and feral, with his hair's white streak expanding. His primary weapon is a customized three-section staff with retractable blades, mastered through self-training. After sealing the powerful relic Ark of Sirius into his right eye, he gained unspecified new abilities.

His journey evolves him from a solitary avenger to an integrated team member. Early on, he distanced himself from the Jaegers to protect them while pursuing the Ark, reflecting his self-sacrificing nature. Confronting his father Alexei's spirit revealed Alexei had sacrificed himself to seal the Ark years earlier. This pivotal revelation shifted Yuliy's focus from vengeance to preventing further suffering, seeking to reseal the Ark without sacrifice. His path culminates in renewed alliances and a commitment to combating supernatural threats beyond his personal vendetta.

Additional details include sensitivity to cold causing frequent childhood sneezing, his left-handedness, self-taught combat skills, and hobbies like plant observation. His favorite subject is biology; he favors foods like sashimi and mandarins without particular dislikes.