Nin-Nin, a dwarfish ninja of the Miroku clan, serves as a subordinate and retainer to Miko Mido. Consistently depicted as hooded and diminutive, he exhibits persistent lecherous behavior. He frequently attempts unsolicited physical contact with female ninjas, especially Miko, often resulting in violent retaliation. His actions include peeping on Miko during private moments like bathing or masturbation, and he visibly delights in encountering her undressed or engaged in sexual activity.

Despite these overtly perverted tendencies, Nin-Nin demonstrates unwavering loyalty to Miko, acting as her protector and striving to aid her in peril. He is dedicated to video recording Miko's encounters, particularly her battles and sexual exploits, providing an in-universe justification for documentation as footage intended for her later review and technique study.

A significant character development reveals Nin-Nin is actually a young Shikima demon. He undergoes a transformation, attaining a mature and physically adult form. This metamorphosis reshapes his interactions within the group, notably attracting sexual interest from both Miko and Fubuki due to his new appearance.