Mao Nanjō is a second-year high school student and classmate of Keiki Kiryū. She sports reddish-brown hair cut to chin length, reddish-hazel eyes, and stands 159 cm tall, typically seen in her school uniform accessorized with baggy socks and a green or blue hair ribbon. Presenting as introverted, quiet, and passive, Mao often appears as a loner with limited social interactions outside her close friendship with Keiki and Shōma Akiyama. Despite her reserved nature, she exhibits greater openness around Keiki, occasionally displaying tsundere tendencies like pinching or jabbing him when flustered and demonstrating concern for his well-being—such as staying with him in the nurse's office after he collapsed. Her background includes serving alongside Keiki on the library committee in earlier school years; an incident where he voluntarily took over her duties ignited her longstanding, concealed romantic feelings toward him. She frequents arcades with Keiki and Shōma, showcasing notable skill in shooting and fighting games by outperforming them. A significant aspect is her secret identity as a fujoshi. She creates and publishes Boys' Love doujinshi under the "Shortcake Series" title, using Keiki (nicknamed "Cake-kun" via a name pun) and Shōma as character models. To gather material, she actively encourages Keiki to enter a romantic relationship with Shōma, even pleading directly. This secret causes a temporary rift upon discovery, though they reconcile after her confession. Her romantic feelings manifest indirectly, noted by others like Shōma observing her frequent stares at Keiki—interpreted as romantic interest. She contemplates confessing multiple times but fails due to Keiki's obliviousness or her own hesitation. Internal conflict intensifies as she considers abandoning fujoshi activities for a conventional relationship with Keiki, particularly after recognizing how her secrecy damaged their friendship, leading to self-blame for lacking courage. Her interactions reveal a complex dynamic: initially exploiting Keiki and Shōma creatively, she gradually prioritizes her genuine affection for Keiki. She provides him relationship advice—including insights about accepting others' unconventional traits—which inadvertently helps him navigate conflicts involving other characters' fetishes. Her development centers on this tension between her BL passions and authentic romantic aspirations.