Yūgo Ōkami, a second-year high school student, is the younger brother of Nana Ōkami. He possesses a large build and stands tall, with dark brown hair and brown eyes. His typical outfit is his school uniform: a collared white long-sleeved shirt, black pants fastened with a brown belt, and gray shoes.

Yūgo cares deeply for his elder sister, frequently visiting her apartment. He exhibits a protective nature toward her, sometimes resorting to violence if he perceives her to be threatened, though Nana disapproves of this behavior. He shares Nana's fondness for cats.

Initially, Yūgo displays hostility toward Subaru Mikazuki, misunderstanding Subaru's intentions and believing him to be a danger to Nana. After this misunderstanding clears, Yūgo recommends Subaru read "Shining in the Dark of Night," unaware that Subaru is the novel's author. Learning this truth—especially after Nana obtains a signed copy—causes Yūgo significant embarrassment.

Determined to apologize, Yūgo visits Subaru's residence but hesitates outside. He encounters Subaru's editor, Atsushi Kawase, who facilitates an introduction. Upon entering, Yūgo attempts to kneel in apology but is stopped by Subaru, who dismisses the incident. During this meeting, Yūgo expresses admiration for Subaru's work, crediting it with giving him courage, and pledges his continued support.

Yūgo's imposing stature sometimes leads others to mistake him for a delinquent or criminal, particularly when seen loitering near Subaru's home. His surname "Ōkami" uses the kanji for "push" (押) and "defender" (守), while his given name "Yūgo" combines "excellence, superiority, gentleness" (優) and "corpse" (伍).