Tomohiro Nagatsuka is a high school student who emerges as a foundational friend in Shoya Ishida's life. Having spent elementary and middle school friendless, often eating lunch alone, Nagatsuka experienced profound isolation and loneliness. This changed when Ishida intervened during an attempt by bullies to steal Nagatsuka's bicycle; Ishida offered his mother's bicycle instead, which was subsequently stolen. Nagatsuka later discovered and returned the stolen bicycle to Ishida's home, an act that initiated their close bond. Nagatsuka swiftly declared Ishida his best friend, affectionately nicknaming him "Yasho" or "Yaeko," and became the first person Ishida trusted enough to remove the symbolic "X" mark representing his social barriers. Physically, Nagatsuka possesses a short, stocky frame and distinctive fluffy, curly green hair. His typical attire includes a yellow jumper layered over a white shirt and a red undershirt, often complemented by a scarf. He has brown eyes and occasionally grew a mustache as a token of luck for Ishida. Nagatsuka exudes a lively, enthusiastic personality marked by strong loyalty and a sense of justice. He is supportive and caring, frequently using humor to defuse tension, though he can also display possessiveness and jealousy, particularly concerning Ishida's interactions with figures like Satoshi Mashiba. Underlying insecurities from past rejections fuel an inferiority complex, sometimes prompting him to lie about his social connections or knowledge for effect. Despite these tendencies, he shows self-awareness and capacity for growth. Ambitious about filmmaking, he persistently pursues this dream despite academic struggles, entering film competitions and later studying film in college. Nagatsuka plays a key mediating role within Ishida's social circle. He facilitates Ishida's reconciliation with Shoko Nishimiya by defending him against her sister Yuzuru's hostility, even physically confronting Yuzuru. Following Ishida's coma after Shoko's suicide attempt, Nagatsuka bonds with Shoko in the hospital where she expresses a desire to continue their film project, forging an independent friendship. His relationship with Naoka Ueno is strained due to a misunderstanding involving a misplaced love letter intended for Ishida; Nagatsuka's mistaken confession to Ueno results in harsh rejection, causing him visible fear around her, though their animosity diminishes over time. Nagatsuka maintains playful, teasing dynamics with Yuzuru and eventually forms friendships with Mashiba and Miki Kawai despite initial jealousy. His development reflects increasing emotional maturity. Progressing from clingy and overbearing tendencies, Nagatsuka learns to prioritize his friends' well-being. He remains steadfastly loyal to Ishida after learning of his past bullying and supports Shoko during Ishida's coma. Though unsuccessful, his film project catalyzes group cohesion and personal resolve, symbolizing his shift from seeking validation to embracing genuine creative passion. The name Tomohiro combines "friend" (友) and "wide, vast" (宏), reflecting his role as a foundational friend, while Nagatsuka means "eternal" (永) and "bundle" (束), suggesting enduring connections.