Ayu is a rather short, strange, energetic, and a very mysterious girl who literally bumps into Yuuichi early in the story of Kanon. She is easily recognizable by her winged backpack, and her red hairband. Ayu is left handed and loves to eat taiyaki. Ayu often takes out her frustration by using the word "uguu."
She met and befriended Yuuichi when they were kids. She fell out of a tree and hit her head on the last day Yuichi was going to be in town. At first, he believes she died, but Akiko reveals she is in the hospital and has been in a coma for the past seven years. The Ayu Yuichi has been meeting in town is actually an astral projection of herself. Later on in the series, she breaks out of her coma, and gets her hair inadvertently cut too short when she goes to a barber shop, leading him to comment how much she looks like a boy like he did before.