Souma Kanzaki is a 16-year-old student raised within the traditional samurai heritage of the Kanzaki family, descendants of the Genji/Minamoto clan. His family, including his parents, younger brother, and horse "Saigo-don," instilled values of honor and virtue. This upbringing leads Souma to carry a traditional Japanese sword and adhere to conventional speech and behavior. From childhood, he exhibited a notably good-natured, earnest, and independent character, requiring little parental attention. Serious, rigid, and quick to jump to conclusions, Souma often instinctively reaches for his sword when emotions flare, particularly towards those he perceives as dishonest. He readily admits mistakes but reacts with intense self-blame, sometimes offering seppuku in apology, followed by rigorous training sessions. Despite his old-fashioned values, he joined the academy's suspicious Marine Bio Club out of deep respect for its president, Kanata Shinkai. He frequently visits aquariums with Kanata, excitedly learning about different fish. However, he clashes with fellow club member Kaoru Hakaze due to their opposing values, maintaining a generally negative view even after gaining some understanding. He shares a close friendship with classmate Adonis Otogari, often jogging together in the mornings. Defined by sincerity and emotional depth, Souma embodies samurai ideals like honor, justice, and honesty, despising deception. Diligent and hardworking, he feels lost during unstructured time. His routines include morning jogs with Adonis, sword practice in the family dojo, and preparing bento meals. He excels academically except in English and is skilled in traditional arts like calligraphy, tea ceremony, flower arranging, and cooking—particularly Japanese cuisine, though he practices others to accommodate friends. His rigid worldview struggles with nuance, sometimes making him appear naive or lacking common sense. He idolizes those kind to him, like Kanata and Keito Hasumi, trusting others easily and displaying a willingness for self-sacrifice without considering his own well-being. This emotional intensity often leads to impulsive actions, yet he remains deeply proud of his heritage. As a member of the unit AKATSUKI under Rhythm Link, Souma demonstrates fierce loyalty to his seniors, Keito Hasumi and Kuro Kiryu. He informally assists Keito with student council work, bringing tea or offering shoulder rubs during stress. He trains obsessively to support them, undertaking extreme methods like sitting under waterfalls or fighting bears. Across stories, he evolves from viewing himself as a novice idol reliant on his seniors towards seeking ways to independently contribute to AKATSUKI. He studies English diligently to expand the unit's global reach, practicing hard to pronounce company names correctly. His performances are described as clean, serious, vibrant, and elegant, accompanied by a smooth, earnest singing voice. Souma's growth is marked by increasing confidence in his identity. Initially burdened by fears of holding back his unit or family, he pushes to become an idol "who shines like the radiant sun." He takes pride in mentoring newer members like Ibuki Taki, who notes Souma's deep love for AKATSUKI and enjoyment in teaching Japanese culture. Despite ongoing struggles with self-doubt and past suffering caused by conflicting loyalties, he focuses on the present, striving to connect his heart to those suffering worldwide through his performances. He declares readiness to cut down any obstacles facing AKATSUKI, aiming for a radiance "that even the sun will envy."