Miyuki Ayukawa is a central figure in the Basquash! series, functioning as the childhood sweetheart of the main protagonist Dan JD and the dedicated mechanic for Team Basquash. She is a teenage girl with a dark complexion, magenta eyes, and dark curly hair styled in dreadlocked twin tails tied with pink ribbons, often accompanied by a bandage on her left cheek. Her background is marked by a difficult childhood: she lived with Dan until her family moved away to the lunar city of Mooneyes, and she later witnessed her father's death in an explosion. She eventually returned to Rolling Town alongside her grandfather at the start of the series, reconnecting with Dan and his sister Coco.

In terms of personality, Miyuki is described as caring, resilient, meticulous, and passionate. She often displays a tough exterior but harbors a deep affection for her team and her childhood friend. Despite her own romantic feelings for Dan, she steps aside when she recognizes the growing mutual attraction between Dan and Rouge, accepting the situation without bitterness. Her motivations are rooted in supporting Dan's dream and keeping the team's Big Foot mecha in peak condition. She is not a Basquash player herself, but she is an irreplaceable part of the team, providing mechanical expertise and upgrades.

Miyuki's role in the story is primarily that of the team's skilled Big Foot mechanic. Upon her return, she teaches Dan how to pilot a Big Foot and later redesigns the team's machines, making them more flexible and agile to the point of being able to create afterimages. She works happily on the Big Foots, finding satisfaction both in helping the team and in earning income for her work. Additionally, she maintains an internet blog under the alias "Ultimate Bystander," documenting Team Basquash's activities with notable accuracy, reflecting her close involvement with the team even from a distance.

Her key relationships center on Dan JD, whom she has known since childhood and for whom she harbors unspoken romantic feelings, and Coco JD, Dan's sister, who is also a childhood friend. Her bond with the rest of Team Basquash is one of mutual reliance and respect. Over the course of the series, she demonstrates significant development in her mechanical skills, progressing from a capable repairer to an innovator who fundamentally improves the team's equipment. Her notable abilities lie in her expertise with Big Foot mechanics, her talent for problem-solving under pressure, and her perceptive understanding of the people around her.