Fuyuki Miyauchi is a supporting character from the anime series Mizuiro Jidai, which is also known by the English title Aqua Age. He is a student and a friend of the main character Hiroshi Naganuma. Fuyuki is often called by his nickname, Miyau, and is rarely referred to by his full name.

His background includes a birthday of March 7, making him a Pisces, and his blood type is O. He stands 153 centimeters tall and weighs 42 kilograms. In terms of his personality, Fuyuki is described as quiet, kind, and gentle. He is considered one of the purest characters in the series and is known for giving good advice to others.

As the class president, Fuyuki holds a position of responsibility at school. His role in the story is largely as a supportive friend. He develops a romantic interest in a girl named Yuko Kawai, the protagonist of the series, falling in love with her at first sight upon seeing her at the entrance ceremony. His feelings for her are inspired by the way she fell and got up, and one episode of the anime is dedicated to exploring his crush called Miyau's Crush. Despite his feelings, the reasons for his specific attraction to Yuko are not deeply explored in the original source material.

Regarding his key relationships, his most significant one is his friendship with Hiroshi Naganuma. He was also friends with a girl named Tomoko Tobita during elementary school, though they became distant after entering middle school. There is no available information about detailed character development across the series or any notable abilities he possesses. Information regarding his specific story-driven motivations is also not available.