Denjiro, also known under the alias Kyoshiro, is a central figure in the conflict of Wano Country. Originally one of the Nine Red Scabbards, the loyal retainers of the Kozuki Family, his life was irrevocably changed by the execution of his master, Kozuki Oden. In the immediate aftermath of that tragedy, Denjiro was consumed by a rage and despair so profound that he secluded himself in an abandoned shack. Over a period of mourning that stretched from autumn into winter, his intense emotions physically transformed him, altering his facial structure, shattering his glasses, and turning his hair from its original dark color to a light blue or white.

Emerging from this seclusion with a new face, he adopted the name Kyoshiro and returned to the Flower Capital, where no one recognized him. Using his cunning and skills, he quickly established himself in the criminal underworld, founding a yakuza group known as the Kyoshiro Family. His power and influence grew to the point where he caught the attention of the shogun, Kurozumi Orochi. Denjiro, now as Kyoshiro, made the painful decision to pledge his allegiance to his master's usurper, becoming Orochi's trusted money changer and bodyguard. This act was the foundation of a twenty-year undercover mission, where he hid his seething hatred behind a mask of loyalty.

The personality Denjiro presents as Kyoshiro is a carefully constructed facade. He appears as a cheerful and self-indulgent man who loves to drink. While intoxicated, he is known for speaking bluntly, openly mocking Orochi's fears and paranoia, a behavior that paradoxically only strengthened the shogun's trust in him. He is prone to dramatic mood swings, from loud laughter to sudden intensity, and is famously known as Napping Kyoshiro due to his habit of falling asleep in public. This drowsiness is actually a consequence of his actions at night, for under his true identity, Denjiro became the mysterious thief Ushimitsu Kozo, or the Witching Hour Boy. Under this alias, he would rob the corrupt wealthy citizens of the Flower Capital and distribute the stolen wealth to the impoverished people living in slums like Ebisu Town, earning him the silent adoration of the common folk.

His true loyalty to the Kozuki family never wavered. One of his most significant acts as a hidden protector was taking in Kozuki Hiyori, Oden's daughter, after she was separated from her guardian. He brought her into the geisha district and raised her, granting her the identity of the renowned oiran, Komurasaki. For thirteen years, he ensured her safety while they both waited in plain sight for the promised day of revenge. Despite his immense hatred for Orochi, Denjiro demonstrated extraordinary emotional control. He endured the humiliation of bowing to his enemy and even acted as his bodyguard, famously intervening to block a powerful slash from Roronoa Zoro that was aimed at the shogun, maintaining his cover at a critical moment. The same stoicism was required when he was forced to smile as Orochi executed his own ally, Shimotsuki Yasuie.

Denjiro's relationships are defined by his unwavering loyalty. His oldest and most trusted comrade is Kin'emon, whom he has known since before they joined Oden, and he holds his friend in very high regard. His bond with Hiyori is that of a protector and a paternal figure, having dedicated over a decade of his life to her safety. His role among the Nine Red Scabbards is crucial; while others traveled through time or hid in remote regions, Denjiro was the one who infiltrated the enemy's heart. His development throughout the Wano Country arc is the culmination of twenty years of patience and sacrifice. When the final battle against Kaido and Orochi began, he unmasked himself, revealing his true identity to his fellow scabbards and finally joining the raid on Onigashima, ready to exact his long-awaited revenge.

In terms of abilities, Denjiro is an exceptionally powerful samurai. He is a master swordsman, shown to be skilled enough to easily block and parry attacks from Roronoa Zoro, a fighter of tremendous renown, with one sword. He is also a proficient user of Haki, the spiritual energy that allows users to surpass human limits. He has demonstrated mastery of Ryuo, a Wano-specific advanced form of Armament Haki that he likely learned while training under Oden. Beyond his combat prowess, his greatest weapon is his intelligence and cunning. He formulated and executed a complex, two-decade-long deception, outwitting a paranoid shogun and his allies while orchestrating a network of theft and charity, all to secure the future of the Kozuki clan.