Nagomi Kinoshita is the paternal grandmother of Kazuya Kinoshita and the matriarch of the Kinoshita family. She is the co-founder and owner of the family liquor store, Nagomi Sake. After her husband passed away, she continued running the store on her own despite being burdened with debt. Her perseverance through these hardships has earned her deep admiration from her family, who regard her as a god-like presence. She is a thin, angular, classy elderly woman with short gray hair and brown eyes.

Nagomi possesses a warm and affectionate personality, though she can also be assertive and sometimes intrusive in her family's affairs. She cares for her grandson Kazuya even more than his own parents do and has always dreamed of him finding a wonderful partner. Despite being an elder, she has a playful and modern side; she enjoys mobile games and even idolizes a game character, often bothering Kazuya with questions about her gaming issues. She also maintains a social media presence to showcase her store and lifestyle.

Nagomi's primary motivation is the happiness and well-being of her family, especially Kazuya's romantic life. Her desire to see him settled with a good partner is so strong that it drives much of the story's central deception. When she meets Chizuru Mizuhara, whom Kazuya introduces as his girlfriend, Nagomi immediately embraces her with open arms. She affectionately calls Chizuru Princess Chizuru and praises her as a goddess for being Kazuya's first real girlfriend. Nagomi actively encourages the relationship and often invites Chizuru to family gatherings, hoping to strengthen their bond.

Her role in the story is that of a catalyst. Nagomi's hospitalization early in the series forces Kazuya to bring Chizuru to the hospital as his fake girlfriend, setting the entire premise of the series into motion. She serves as a constant reminder of why Kazuya and Chizuru must maintain their charade, and her genuine affection for Chizuru creates both pressure and motivation for Kazuya to pursue a real relationship. Nagomi is also a key figure in the Paradise Arc and other major story events, where her presence heightens the stakes for the main characters.

Nagomi shares a close friendship with Sayuri Ichinose, Chizuru's grandmother. This pre-existing bond between the two grandmothers adds another layer to the connection between Kazuya and Chizuru, as both elders deeply wish for the young couple to find happiness together. Nagomi also has a son, Kazuo, and a daughter-in-law, Harumi, though her relationship with Kazuya is notably the most affectionate and involved in the family dynamic. She is often exasperated by Kazuya's parents but remains the emotional center of the Kinoshita household.

Over the course of the series, Nagomi shows little personal development in the sense of changing her worldview, but her role evolves. She remains a steadfast, loving presence who never wavers in her support of Kazuya and her hope for his future. Her health is fragile, and she has been hospitalized multiple times, which makes the family deeply concerned about her well-being. This fragility adds urgency to her desires and raises the emotional stakes for Kazuya, who does not want to disappoint her.

Nagomi does not possess any supernatural or extraordinary abilities. Her notable strength lies in her resilience, emotional intelligence, and her ability to create a warm and welcoming environment. She is perceptive and often sees through deception, though her hope for Kazuya sometimes makes her willingly overlook inconsistencies. She is also skilled in running her sake store and managing her household, embodying the traditional values of hard work and family devotion.