Shun Hanamori is a 26-year-old man, 169 cm tall, who serves as an officer in the United Nations Policy Division of the Foreign Policy Bureau at the Ministry of Foreign Affairs. He maintains a carefree and jovial demeanor, frequently joking around and displaying a relaxed attitude that contrasts with his serious colleague, Kōjirō Shindou—even accepting yogurt as a bribe to exchange duties. Despite this easygoing nature, he demonstrates professionalism and takes his work seriously when required. He is emotionally expressive, quick to cry, and prone to worrying about his friends, as seen when he immediately ran to aid Shindou during adverse effects from initial exposure to the anisotropic.

Though often meek, he possesses a reliable and competent side, handling responsibilities effectively when necessary. After Shindou declined the role, Hanamori assumed the position of the Japanese government's negotiator to the anisotropic being Yaha-kui zaShunina, a change that left him overwhelmed with the resulting workload.

He is gay and in love with his friend and colleague Kōjirō Shindou; this aspect of his character is presented straightforwardly, without stereotypical mannerisms, though he is notably clingy in his interactions with Shindou.

A significant part of his development involves becoming a parental figure. He was entrusted with raising Shindou and Saraka Tsukai's daughter, Yukika Shindou, from infancy through her teenage years while her parents were occupied with events related to the Kado incident, serving as her primary caregiver and parental substitute for a substantial period.