Nonohana Miyoko, also called Miyo-chan, is an intelligent child character who attends school alongside the protagonist Kiteretsu. Boys widely admire her for her intellect and demeanor. Her name originates from the Toyama dialect, where "Miyo" means "person is beautiful."

Miyoko shares a notably close relationship with Kiteretsu, serving as one of his best friends and acknowledged love interest. The series indicates she harbors a subtle crush on him, though this remains understated. Several time travel episodes depict her as Kiteretsu's future wife, suggesting their destined long-term connection. Her family includes a father, a working professional who relocated to Hokkaido; a homemaker mother; and an elder brother pursuing university studies in Hakodate.

Miyoko exhibits loving, caring, and kindhearted personality traits and shares a documented fondness for sweet potatoes. Her compassionate nature and intellectual disposition draw comparisons to Shizuka Minamoto from the Doraemon series. Visually, she possesses neck-length brown hair and black eyes, contributing to her resemblance to Michiko Sawada from the Perman series, though their personalities differ.

She participates in various adventures involving Kiteretsu's inventions, including time travel expeditions. Miyoko holds the distinction of being the second protagonist to perform the series' introductory theme song.