Kemuzou Kemumaki, a cunning Koga ninja entrenched in the historic Iga-Koga clan feud, relentlessly opposes his sworn rival Kanzo Hattori. Fueled by a bitter rivalry with Kenichi Mitsuba for classmate Yumeko Kawai’s affections, he devises intricate schemes involving elaborate disguises, deceptive ploys, and advanced gadgets to outmaneuver both Kenichi and Hattori. Though often self-serving, Kemumaki sporadically reveals vulnerability—collaborating with Hattori to save his cat Kagechiyo or mentoring Shinzo Hattori in techniques like water-walking.

Short and stocky with spiked black hair, freckles, and signature green ninja garb, he dons a blue jacket and trousers casually. His personality oscillates between brash ambition and hesitant insecurity, particularly when outmatched by Hattori’s prowess or foiled by his own miscalculations. Kagechiyo, his sharp-tongued feline partner, remains loyal yet unafraid to challenge his harsher impulses.

In crossover events like *Ninja Hattori-kun + Perman: Chō-Nōryoku Wars*, Kemumaki plunges into chaotic battles, clinging to his trademark antics. During a clash with Psychoman, he launches remote-controlled planes to dazzle Yumeko, only to trigger a fiery mishap when debris ignites his head. Later, he seethes as Yumeko and psychic Yuri shower Kenichi with attention, his jealousy laid bare.

Adept in ninjutsu, combat, and mimicry, he masquerades as Hattori, Kenichi, or even Yumeko to sow discord. Yet his overconfidence often backfires—trapped in a canine disguise intended to trick Yumeko, he briefly embraces the ruse after noting its perks.

Living alone in an apartment with no known family, Kemumaki attends school alongside Kenichi and Yumeko. While Mr. and Mrs. Mitsuba perceive him as polite, his true nature surfaces in oscillating alliances—alternately scheming against rivals and forging uneasy truces, embodying a paradox of rivalry-driven mischief and sporadic camaraderie.