Yoshiyuki Hatori is a central narrative figure and second editor-in-chief at Marukawa Publishing's Emerald department, renowned for exceptional professional competence and efficiency. He mentors colleagues like Ritsu Onodera, advising on workplace challenges and interpersonal dynamics. His lifelong bond with manga artist Chiaki Yoshino began in childhood, extending through shared schools and university. During university, Hatori pledged academic support for Chiaki’s manga pursuits, later deliberately becoming a manga editor to champion Chiaki’s professional career.

Hatori displays a consistently calm, serious demeanor professionally and personally, excelling at domestic tasks like cooking and housekeeping for Chiaki. Beneath his reserved exterior lies deep care for loved ones, though complicated by jealousy and internal conflict regarding Chiaki. He avoids confrontations, dislikes sweet foods, and maintains composure in most situations.

Their relationship evolves from friendship to romance through intense emotional trials. Hatori concealed romantic feelings for years, fearing their bond’s destruction. His non-consensual kiss during Chiaki’s sleep—depicted with heightened intensity in light novels—triggered mutual confusion and estrangement, worsened by Chiaki’s mistaken belief in Hatori’s involvement with mutual friend Yuu Yanase. Hatori attempted withdrawal over guilt, but Chiaki initiated reconciliation, cementing their committed relationship.

Persistent insecurities and external complications challenge them, including Yuu Yanase’s unresolved romantic attachment to Chiaki. Hatori and Yuu share tense coexistence since middle school, masking mutual animosity for Chiaki’s sake while acknowledging each other’s professional skill. Despite friction, Hatori prioritizes Chiaki’s wellbeing, occasionally requesting Yuu’s assistance with Chiaki’s manga.

Hatori later doubted Chiaki’s romantic authenticity, attempting to end their relationship. Chiaki countered by firmly asserting genuine love, strengthening their bond through shared commitment. By the anime’s second season, they navigate ongoing misunderstandings after one year of dating.

Professionally, Hatori maintains loyal, effective collaboration with superior Masamune Takano, consistently meeting deadlines and author-management expectations. He mentors newer colleagues like Onodera with practical guidance. Personal details include being an only child, childhood shortness compared to Chiaki, the nickname "Tori," and prior use of Chiaki’s first name before mutual adoption of formal address.