Yūto Ayase, an ordinary second-year student at private Hakujō Academy, lives with frequently absent parents and his older sister Ruko, who serves as the primary adult figure despite her professional role as a private secretary. Yūto manages most household chores due to Ruko's incapacity for housework. He maintains a blunt demeanor, prefers solitude, and achieves average academic performance that later improves through tutoring.

His life shifts dramatically upon accidentally discovering classmate Haruka Nogizaka’s secret passion for anime and manga in the school library. After promising to keep her secret due to her past ostracization, they form a close friendship. This bond sparks jealousy among male classmates and positive attention from female peers, partly influenced by his sister Mika frequently discussing him at her all-girls school. Yūto regularly accompanies Haruka on trips to Akihabara and other otaku activities, gradually engaging more deeply in her world despite his initial lack of expertise.

Yūto initially struggles with feelings of inadequacy about his middle-class background compared to Haruka's wealth, believing it prevents formal dating. This insecurity surfaces during events at her estate, though he eventually accepts her family's approval, including her father Gentō's reluctant tolerance. His protective nature drives him to defend Haruka’s interests multiple times—confronting Gentō over her hobbies and later assisting her against former middle school friends who shunned her.

Yūto’s character evolves through challenges. He temporarily serves as a butler for wealthy first-year Tōka Tennōji ("Princess Blizzard") to fund Haruka’s Christmas gift, earning recognition for his endurance and butler skills. His resolve is tested when transfer student Shiina Amamiya, Haruka’s piano rival, confesses feelings during a class trip to Hokkaido. After hesitation, Yūto reaffirms his commitment to Haruka, leading them to secretly become a couple to avoid school gossip. Their relationship culminates in marriage after Yūto intervenes in Haruka’s arranged wedding, storming the ceremony with allies including Mika, family maids, and Shiina—later revealed as a test by Haruka’s parents to confirm his dedication.

Throughout events, Yūto demonstrates unexpected household skills and earns nicknames like "Ero-megane" from accidental compromising situations. His quiet determination and rhetorical abilities during crises earn respect from figures like Gentō. A pivotal revelation shows he unknowingly sparked Haruka’s otaku interests years earlier by giving her a manga volume during distress. He proves adept at navigating conflicts involving Haruka’s admirers or family opposition, resulting in their marriage and future life with two daughters.