Kanami Etō is a 13-year-old second-year middle school student at Minoseki Academy, renowned as one of her generation's strongest sword fighters. She sports short brown hair often tied in a small ponytail and light-brown eyes, typically dressed in her school uniform, black thigh-high socks, and running shoes. Her personality radiates cheerfulness, optimism, and a deep passion for kenjutsu, especially evident during matches where she delights in opponents' tactics. While impulsive in pursuing challenging fights, she possesses a strong moral compass, kindness towards adversaries, and the maturity to acknowledge her mistakes. Beneath her energetic exterior lies notable observational skill and perceptiveness.

Her background includes an unnamed father, an older brother, and a deceased mother who was a highly skilled Toji, establishing Kanami as a generational talent mirroring her mother's legacy. Her enrollment at Minoseki Academy forged a close friendship with classmate Mai Yanase prior to the series' events.

During the national swordsmanship tournament at the Origami estate, Kanami became the Minoseki Academy champion after defeating Mai Yanase in the finals, following victories over opponents like Renpu Girls' School's Sayaka Itomi. In the decisive match against Heijou Institute's Hiyori Juujou, Kanami intervened to protect Hiyori from the Origami Elite Guard when Hiyori attacked Yukari Origami, driven by her desire to continue their unfinished duel and her observation of an Aradama concealed within Yukari's hair. She subsequently aided Hiyori's escape from Kamakura to Tokyo, evading pursuers through hitchhiking and frequent location changes. Although tracked down via a phone call to Mai, Kanami and Hiyori escaped capture, later reuniting with Mai during an Aradama incident in Tokyo where Mai allowed them to leave freely.

Their journey continued with a stay at Rui Onda's apartment, followed by an encounter with Sayaka Itomi, whom they defeated and confirmed as non-hostile. Guided toward Irozaki, they traveled to Ebisu, where Hiyori temporarily abandoned Kanami over doubts about her commitment to assassinating Yukari. Kanami fought Osafune Girls' Academy members Kaoru Mashiko and Ellen Kohagura alone until Hiyori returned, solidifying their partnership. After learning about the Great Disaster of Sagami Bay and Yukari Origami's true nature from Hiyori, they encountered Kaoru and Ellen again, who revealed their affiliation with the anti-Origami group Mokusa. Joining Mokusa led to an ambush by Elite Guard Yomi Satsuki, resulting in a battle against Elite Guards Maki Shidou and Suzuka Konohana. Kanami initially struggled against Suzuka's aggression but executed a coordinated counterattack with Hiyori to escape. Later, upon returning to Ebisu to rescue Ellen, they confronted the Noro-enhanced Yomi and narrowly escaped when Yomi lost control, leading to their extraction via a Mokusa submarine.

In combat, Kanami exhibits masterful swordsmanship, winning the Minoseki championship and holding her own against elite opponents like Suzuka Konohana. Her primary style is Yagyu Shinkage-Ryu, emphasizing predicting opponents' movements and utilizing techniques like the "Bladeless Takedown." She possesses immense speed enabling near-infinite speed Jin'i, exceptional stamina for sustained battles, and formidable willpower allowing her to fight through extreme fatigue, notably against the Great Aradama Tagitsuhime. Extensive training has developed superior instinct, subconscious fighting efficiency, and keen insight to identify sword styles and personalities through combat. Her extensive kenjutsu knowledge lets her recognize, counter, or replicate techniques, and her tactical intellect allows real-time strategy adjustments and psychological manipulation. She also maintains prolonged Utsushi activation.

Her designated okatana is Chidori, a short, curved blade leaving a distinctive white trail when swung. The sword symbolizes freedom and achieving the impossible, demonstrated when it cut through lightning during her battle against Hiyori fused with Princess Ichikishima, reflecting her character growth and legendary connection.

In the chibi spin-off "Mini Toji," Kanami retains her core traits—cheerfulness, fencing enthusiasm, and strength—within a comedic, school-life context. Her interactions with characters like Hiyori and Mai continue in a lighter tone focused on daily activities rather than combat.

Her key relationships include a close bond with Mai Yanase, embodying a tomboy-girly girl dynamic, and a complex partnership with Hiyori Juujou that evolves from rivalry to mutual reliance. She influences Sayaka Itomi's development through their duel and encounters. Her connection to her late mother serves as both inspiration and a legacy she upholds through her skills and determination.