Age: 15
Birthday: November 22nd
Height: 155 cm (5'1")
Weight: 43 kg (94 lbs)
Blood type: B
Songs: Ayano's Theory of Happiness (アヤノの幸福理論, Ayano no Koufuku Riron), Transparent Answer (Toumei Answer), Lost Time Memory, and Additional Memory
Eye Ability: Favoring Eyes
First appeared in Transparent Answer. A cheerful girl who was Shintarou's classmate. In the summer of her first year of high school, she made contact with Shintarou, who had a tendency to keep a distance, but who soon relented to her advances and genuinely enjoyed her company. From then on the two became close friends. Shintarou catches her crying one day but is at a loss at what to do and leaves. The next day it is revealed that she had committed suicide for some unknown reason.

Jin's eleventh song, Ayano's Happiness Theory revealed that she is the original founder of Mekakushi Dan (labeled as member no.0) The other three members, Kano, Kido and Seto were adopted by Ayano's mom to the Tateyama household at a young age. Being the big sister, Ayano tried to get along with the three children using many means. Then she decided to make a secret group and even gave them hoods. When they were teenagers, Ayano's mom passed away, and from then on, things went haywire. Her father was scheming to experiment on two of Ayano's school friends, Takane and Haruka. It is then revealed that one can obtain red eyes when exposed to a near-death experience. Believing that by obtaining red eyes she would stop the Snake of Clearing Eyes from fulfilling its plan, she committed suicide.
After committing suicide, she was possessed by the Favoring Eyes snake, which allows her to project her emotions onto others.
During the true ending, Shintarou enters the Heat Haze and informs her of her ability. Together, they leave the Heat Haze and confront the Snake of Clearing Eyes. She projects Shintarou's memories into Mary, stopping her from resetting time again.
(Source: Vocaloid Wikia)