Miharu Amakase is a student at Kazami affiliated junior high, one year younger than the main characters Nemu Asakura and Junichi Asakura. She is a childhood friend of both, having become close after Sakura Yoshino left the island. Miharu is known for her energetic and enthusiastic personality, which often overrides her common sense. She has a deep affection for Nemu and behaves much like an adoring puppy around her, earning her the nickname Doggy. Miharu is also famously fond of bananas, especially chocolate-covered ones, and she can often be seen eating them.

A significant aspect of Miharu's story involves an android double that was created by her father, Professor Amakase, after the real Miharu suffered a serious accident and fell into a coma. The android, which looks identical to Miharu, experiences the world for the first time with childlike wonder and enthusiasm. It is prone to circuit overloads when overly excited, requiring Junichi to discreetly intervene. The android shares the same love for bananas and a similar devotion to Nemu. During the events of the first season, the android eventually reaches the end of its life expectancy, and the real Miharu awakens from her coma, reuniting with her friends in the second season. Miharu is often innocent and forgetful in her remarks, but she can also display a surprising sense of responsibility. She is unaware that Nemu and Junichi are step-siblings and cheerfully supports their relationship from a distance. Miharu does not possess any supernatural abilities; her notable traits are her unwavering loyalty, her boundless energy, and the unique circumstance of having been temporarily replaced by a robotic counterpart.