Shusuke Fuji is a third-year student and tennis team regular at Seishun Academy, born on February 29th. Standing 167 cm tall and weighing 53 kg with blood type B, he possesses honey-brown hair framing a pale, slender face with a pointed chin. His eyes remain characteristically closed when smiling, yet reveal sharp blue (anime) or light brown (manga) irises in moments of seriousness or provocation. Originally from Chiba, he now lives in Tokyo with his mother Yoshiko (49). His family includes an unnamed father working overseas, older sister Yumiko (24), and younger brother Yuuta, who attends St. Rudolph. Fuji maintains a deeply protective bond with Yuuta, reacting decisively to threats against him, such as his victories over Akutagawa Jirō and Mizuki Hajime. He similarly defends injured friends like Tachibana Kippei and Echizen Ryoma, targeting perpetrators like Kirihara Akaya, though he rarely exhibits anger over personal slights. Nicknamed "Tensai" (genius) for his tactical skill, Fuji employs a counter puncher style. His initial Triple Counters – Tsubame Gaeshi (Swallow's Return), Higuma Otoshi (Brown Bear Drop), and Hakugei (White Whale) – proved inadequate against national-level opponents like Tachibana, prompting him to develop Kagerō Zutsumi (Dragonfly Illusion). During the National Tournament, he unveiled Hekatoncheires no Monban (Gatekeeper of Hekatoncheires) against Shiraishi Kuranosuke and a sixth counter against Niō Masaharu. He later refined his original Triple Counters into Huō Gaeshi (Phoenix Return), Kirin Otoshi (Kirin Drop), and Hakuryū (White Dragon). His Disappearing Serve (Kieru Serve) creates optical illusions through spin. Fuji typically plays Singles 2 but partners with Kikumaru Eiji as the "Dream Pair" or with Kawamura Takashi. He briefly alternated in Singles 1 with Echizen during captain Tezuka Kunimitsu's absence. Off-court, Fuji presents a cheerful, easygoing demeanor but enjoys mischievous teasing, revealing a subtly sadistic streak. Popular yet emotionally guarded, his daily routine involves waking at 6:00 AM, tending cacti, calling Yuuta, attending practice, and studying classical literature. He favors unconventional foods like wasabi rolls, spicy ramen, and honey-mustard, tolerating most of Inui Sadaharu's penal drinks except the cod liver oil-based Aozu. He excels in non-tennis sports like beach volleyball, winter sports, and curling. Fuji's relationship with Tezuka Kunimitsu is pivotal. As first-years, they defeated seniors together, but Fuji later challenged Tezuka, suspecting a hidden arm injury; his 6-0 victory confirmed it, leading to a promised rematch. Tezuka acknowledged Fuji's longstanding support. Witnessing Tezuka's injury against Atobe Keigo shifted Fuji's motivation from personal satisfaction to preventing Tezuka from bearing excessive responsibility. This culminated during his Nationals match against Shiraishi, where he overcame a 0-5 deficit using evolved techniques despite losing 6-7. This commitment led Tezuka to entrust him with Singles 2 thereafter. At the U-17 Camp, Fuji partnered with Yuuta for a tie-break challenge but defeated him seriously at Yuuta's request. He progressed to Court 6 after defeating high school opponents and observed Court Shuffle matches. His long-awaited rematch against Tezuka occurred after Tezuka unlocked Tenimuhō no Kiwami (The Pinnacle of Heavenly Perfection).