Sanshiro Sugata, a talented but undisciplined youth, arrives in 1882 Tokyo seeking martial arts instruction. Initially drawn to jujutsu, his path shifts when he witnesses judo master Shogoro Yano defend himself against multiple jujutsu practitioners. This demonstration convinces Sanshiro to become Yano's student at the Shudokan Judo school.

Possessing physical prowess but lacking emotional control, Sanshiro's impulsiveness leads to street fighting. Yano recognizes his potential but criticizes his lack of restraint, comparing teaching him to giving a knife to a madman. This harsh critique drives Sanshiro to spend a night immersed in a cold lotus pond. During this ordeal, he gains self-realization upon seeing a lotus blossom bloom. He emerges humbled and seeks Yano's forgiveness, marking a turning point.

Progressing in judo, Sanshiro becomes a leading student. He represents his school in competitions, facing Saburo Kodama, a jujutsu practitioner who previously attacked Yano; Kodama dies accidentally during their match. Sanshiro later fights Hansuke Murai, head of a rival jujutsu school, in a public bout to determine which school trains the local police. Sanshiro wins, injuring Murai significantly. Following this victory, Sanshiro forms a respectful relationship with Murai and develops romantic feelings for his daughter, Sayo.

Sanshiro's interest in Sayo attracts Gennosuke Higaki, another jujutsu master who competes for her affections. Higaki challenges Sanshiro to a duel. Their stormy confrontation culminates in Sanshiro defeating Higaki and inflicting permanent injuries. After this victory, Sanshiro prepares to depart for Yokohama, promising Sayo he will return.

His journey emphasizes the transition from raw talent to disciplined mastery, paralleling the cultural shift from traditional jujutsu to modern judo in Meiji-era Japan. It involves overcoming personal flaws, confronting rivals, and navigating romance.