Kintoki Miyazawa serves as the adoptive grandfather of protagonist Kiichi Miyazawa and is father to Seiko, Kiryuu, Sonou, and Yumiko Miyazawa. Once the 13th head of the Miyazawa clan and master of the Nadashinkage-ryu martial art style, he refrains from openly demonstrating his skills or participating in Kiichi's training, creating ambiguity about his combat capabilities despite his former status and the maintained prowess of other elderly masters.

He maintains a jovial, often perverted demeanor, frequently flirting with older neighborhood women. His daughter Yumiko notes his current lightheartedness contrasts sharply with a past where he was considered terrifying. Physically, he appears as a diminutive, bald figure, usually wearing a skull cap and tracksuit.

As a martial arts master, Kintoki developed specialized techniques like the Centipede Lock. He delegated teaching this to Heizou Onikawa for Kiichi, reasoning personal instruction would be too lenient. He also taught the Kaishuken to Sonou and instructed all his sons in the Bullet Slide technique. He fought multiple battles against Jouichirou Kusakabe, former head of the rival Yuugenshinkage-ryuu style; the outcomes are unspecified, though Kintoki dismissed his son Kiryuu's suggestion of losses as lies.

Latent abilities are hinted at, such as when he mysteriously severed piano strings without visible contact, evidenced only by Kiryuu's surprise and Kintoki's knowing smile. In the PlayStation 2 game *Tough: Dark Fight*, he appears as a playable character using the Kobakushou technique as a special move.