Akihito Sudō is a former captain of the Hokuo Academy karuta club and is two years older than the main characters of the story. After graduating from high school, he attends the University of Tokyo, where he continues to practice karuta as a member of the university’s karuta association. He holds a Class A ranking. Sudō is widely known for having a sharp and often difficult personality, taking pleasure in teasing others and pointing out what they dislike. His behavior can be perceived as harsh or even sadistic. Beneath this prickly exterior, however, lies a deep and genuine love for karuta. His ultimate ambition is to become the president of the Karuta Association. Since all past presidents have also been masters, his current goal is to achieve the rank of master himself. He envisions a future where he holds a normal job while continuing to play karuta into old age, focusing on administrative and operational work so that future generations can enjoy the game with peace of mind—a philosophy he views as a blend of the literary and martial arts.

As a competitor, Sudō is consistently strong. During his high school years, he faced Chihaya Ayase in the team championship preliminaries and lost to her. He became the runner‑up in the individual event at the High School Championships, losing to Shinobu Wakamiya. In the East Japan Meijin qualifiers, he has lost to veteran player Hideo Harada. He attends reader study classes because the Meijin, Hisashi Suō, places great importance on studying the patterns of card readers. As a university student, Sudō becomes one of two people whom Suō primarily practices with. At Suō’s request, he invites Chihaya and Taichi Mashima to practice at the University of Tokyo karuta hall, and he realizes that Taichi harbors romantic feelings for Chihaya. He has also served as a card assistant for Suō’s Meijin title matches.

Sudō has a notable rivalry with Taichi Mashima, having lost to him in a fateful match at the Yoshino Kai and again in the semifinals of the East Japan preliminaries. He has faced and lost to Harada on multiple occasions. Suō values his strength and personality, noting that Sudō is both strong and smart, and that his difficult personality makes him the hardest opponent to suppress. Harada holds him in high regard, praising his leadership and stating that Hokuo Academy’s greatest asset is wanting strong karuta players. Sudō’s playing style reflects his personality; he strategically arranges his cards to disturb an opponent’s psyche, such as placing a favorite card in the center of his own field to draw their focus. His coach at Hokuo notes that if not for his sadistic streak, his potential would make him a formidable Meijin contender. Despite his harsh reputation, others recognize his deep commitment to the game, and Taichi observes that Sudō genuinely loves the world of karuta. Throughout the series, Sudō transitions from a high school rival to a more complex figure in the larger karuta community, showing a willingness to learn and adapt, and taking on responsibilities such as serving as a reader for high school championship matches. He remains a powerful competitor capable of beating strong opponents like Nishida and Rion Yamashiro.