Kōshō Shinogi is a skilled karate fighter and a prominent martial artist within the Baki series. He is the younger brother of Kureha Shinogi, a renowned surgeon, and is known as an expert in a specialized form of karate referred to as cord-cutting or himokiri karate. This style is distinct from conventional striking arts, as its attacks are not blunt blows but rather slashing motions capable of cutting an opponent. Shinogi possesses an extensive knowledge of the human nervous system and circulatory system, and his primary technique involves using his bare hands to sever or disconnect vital nerves and tendons, thereby immobilizing his opponent. This ability has earned him the moniker of the Cord Cutter.

Shinogi's background is marked by a deep and complex relationship with his older brother, Kureha. During their childhood, Kureha excelled in all areas, including academics and sports, and frequently came to Kōshō's rescue. This constant overshadowing instilled in Kōshō a strong sense of inferiority and a powerful drive to prove his own strength independently. This motivation is the core of his personality; he is intensely competitive and seeks to establish his own identity as a formidable fighter outside of his brother's shadow. Despite this, he maintains a respectful relationship with Kureha, though the underlying tension of his inferiority complex remains a central part of his character. In terms of demeanor, Shinogi is often serious and focused, possessing a logical and analytical approach to combat that complements his precise fighting style.

In the narrative, Shinogi first appears as a challenger to the protagonist, Baki Hanma, engaging in a fight during the early Underground Arena saga. Although he is ultimately knocked out by Baki, this encounter establishes him as a dangerous adversary. He later participates in the Maximum Tournament, a major story arc. In the first round of the tournament, he is matched against his brother, Kureha. However, Kureha, after witnessing Kōshō's resilience and determination, forfeits the match rather than fighting him. In the second round, Shinogi faces the veteran jujutsu master Gouki Shibukawa. During this fight, Shinogi manages to break Shibukawa's prosthetic eye, but despite this feat, he ultimately loses the match. This loss does not diminish his standing, and he continues to appear in later arcs, including the Great Raitai Tournament saga, with his role evolving from a primary antagonist into a supporting figure within the broader cast of warriors. His development is largely tied to his ongoing struggle to overcome his brother's legacy and solidify his own reputation.