Mino Nenki is a ninja of the Iga Tsubagakure clan, selected as one of the ten warriors to represent his clan in the conflict against the Kouga Manjidani. He possesses a feral, bestial appearance and demeanor, with a tangled mass of hair that reaches past his waist and a body covered in coarse fur. His pride often leads him to underestimate his opponents, and he acts recklessly in battle, yet his fighting prowess makes him one of Iga’s most formidable fighters. While he generally defers to the command of Yakushiji Tenzen, Nenki does not hesitate to question his authority and sometimes acts independently, seeking to prove his own strength. He is more tolerant of Oboro’s indecisiveness than many of his comrades, viewing her attachment to Gennosuke Kouga as a childish phase that will pass with time.

Nenki’s primary ability is the control he exercises over his own hair. He can straighten and extend it at will, using it to grasp and manipulate objects, swing through trees, or entangle and crush enemies. The hair can be made as rigid as thousands of needles, allowing him to skewer opponents who come too close. Beneath his robes, his body hair can stiffen into a defensive layer, protecting him from certain attacks. He also wields a staff in combat, though his hair remains his most versatile weapon. His pride and aggression drive him to seek glory in battle, and he willingly attacks enemy strongholds without hesitation.

In the conflict, Nenki participates in several key engagements. He is part of the raid on the Kouga village of Manjidani, where he uses his hair to seize and kill enemy ninja. He later pursues the Kouga warrior Okoi, capturing her after a prolonged chase, and ultimately kills her when she attempts to use her blood‑drain technique against him. His overconfidence leads to his downfall when he confronts Muroga Hyouma and Gennosuke Kouga. Believing that Hyouma’s blindness makes him helpless, Nenki is caught off guard when Hyouma opens his eyes and reveals his Dojutsu technique, the power to turn an opponent’s killing intent back upon themselves. Unable to resist the effect, Nenki’s own hair wraps around his body and crushes him to death.

Nenki’s relationships with his fellow Iga are marked by a lack of deference to Tenzen and a blunt, often insulting manner toward others, such as when he jests about Hotarubi’s personal life. He shows no emotional attachment to his clan’s leader, Oboro, viewing her as naive. His loyalty is to the Iga’s cause rather than to any individual, and he fights with a savage pride until the moment of his death. The live‑action film adaptation of the same story reimagines Nenki as a silent, feral beastman with a keen sense of smell and long iron claws, omitting his hair‑based abilities and staff, but in the anime and manga source material his hair manipulation remains his defining trait.