Tetsu Shinjou presents as quiet and reserved, speaking minimally. His tall, imposing frame contrasts a gentle and kind nature, especially toward teammates and children. He patiently mentors younger players, offering deck-building advice and answering game questions. Yet during cardfights, he becomes relentless, openly criticizing opponents who fall short of expected skill levels. His background includes involvement with a high school gang. When gang members brought Ren Suzugamori to their hideout, Tetsu rejected Ren's invitations to play Cardfight!! Vanguard. Only after Ren's persistent efforts did Tetsu agree to a rooftop match. Losing ignited his competitive drive, leading him to demand rematches until he secured victory, cementing his dedication to the game. As a founding member of the Foo Fighters organization alongside Ren, Tetsu earned the title of "General" within Team Asteroid (later AL4). He served as Ren's right-hand man, managing much of the organization's operations due to Ren's apathy. Tetsu was the first subjected to Ren's PSYqualia ability, an incident leaving a lasting impression of Ren's power but strengthening their bond. When Kai Toshiki deserted, Tetsu remained loyal to Ren. Throughout Season 1, Tetsu enforced team discipline, including expelling underperforming members like Yahagi Kyou. He competed in national tournaments, contributing to Foo Fighter victories. During a critical match against Team Q4, he confronted Aichi Sendou about his limitations. Following Asaka's dismissal from Team Asteroid, Tetsu privately expressed a desire to see Ren defeated, believing Aichi capable of achieving it. In Season 2, Tetsu transitioned to a supportive role, relinquishing his tournament spot to Kai. He visited Card Capital to advise Team Q4 on clan developments and warn them about VF Circuit challenges. He continued mentoring younger players like Sendou Emi and repeatedly defeated Kamui Katsuragi, though Kamui eventually won against him while Tetsu was disguised. After graduating high school in Season 3, Tetsu became coach of Fukuhara High School's cardfight club, hosting training matches with Team Dreadnought. He oversaw his club's matches during the VF High School Championship preliminary rounds. Later, a Reversed Kai challenged and defeated him, resulting in Tetsu becoming Reversed. In this state, he defeated Team Brilliant Stars, spreading the Reversed condition. He then awaited Ren on Foo Fighter's rooftop, where they fought a cardfight mirroring their first encounter. During this emotionally charged match, Tetsu reminisced about their past and ultimately defeated Ren, reaffirming their bond by calling him a "Foo Fighter." In the GIRS Crisis arc, Tetsu resurfaced as an employee at the United Sanctuary branch, working as assistant to branch manager Ren Suzugamori. In the V Series continuity, he later lost his connection to Vanguard due to being "deleted" but continued researching PSYqualia, contributing to the development of the VF Gloves used by Foo Fighter cardfighters. Tetsu's expertise extended beyond fighting to deckbuilding. He consistently used Dark Irregulars decks focused on rapid soulcharging to empower key units. His original deck centered on Stil Vampir and Demon World Marquis, Amon, utilizing cards like Dark Soul Conductor for efficient soulcharging. During the VF Circuit, he adapted his strategy to incorporate the Witching Hour series, emphasizing critical triggers and cards like Yellow Bolt for early soulcharging. His manga counterpart employed a distinct strategy revolving around No-Life King, Death Anchor, which exchanged damage zone and soul cards for power boosts. When Reversed, he switched to an Amon-based deck.