- Ayano grew up living with her father Kenjirou and her mother Ayaka, who would often read a book called "The Legend of the Medusa" to her. Although Ayano grew bored with the story at some point, she would keep listening to it, as it was the favorite book of her mother. When Kido, Kano, and Seto were taken in as foster children, she treated them like a real older sister would, because of her natural warm-heartedness and nurturing personality. The children considered themselves monsters, due to their red eyes, so to cheer them up, she eventually asked them to start a gang of heroes with her, stating that red is the color of heroes. Thus, the Mekakushi Dan was created with her being the founder, number "0".
- During middle school, she befriended a boy named Shintaro Kisaragi, who had a tendency to keep a distance to other people and kept a generally negative view on the world, despite his high intelligence. Ayano, who had always been a bad student in comparison, tried her best to change his views, and would do simple things, like turning test results into paper planes for fun, to accomplish that. While his views did not seem to change, Shintaro soon relented to her advances and began to genuinely enjoy her company, resulting in them becoming close friends.
- Eventually, a phone call arrived Ayano and her foster siblings, telling them that their parents were caught in a landslide and that they could not find the body of Ayaka, leaving the children devastated. Ayano began to wonder why bad things kept happening to their family, but promised herself to be strong for her siblings, keeping up her cheerful personality, even after attending the funeral for her mother not long afterwards.
- During her last year of middle school, she discovered notebooks with notes about the "Legend of the Medusa" in her father's office, while she was wandering through the room without his permission to close a window. As she began to read, she began to realize that the legend was not just a story, but a real phenomenon. Hearing her father come home, she quickly hid one of the notebooks under her shirt and carried it to her own room, where she continued to read.
- One day, Ayano and Shintaro visited the school festival of the school Ayano's father was a teacher at, where Shintaro participated in a visual shooting booth hosted by Takane Enomoto and Haruka Kokonose, two students of Ayano's father. Shintaro won against Takane, but declined the grand prize the booth had offered, proceeding to act rudely towards the girl. After he left, Ayano spoke to Takane to apologize for his behavior, and the two of them started to have a conversation, in which Ayano mentioned that her and Shintaro were probably to enroll into this school next year, making Takane her upperclassman.
- At the evening of the festival, Ayano was in her room, as she heard someone wander through the corridor, so she went to see who it was, learning that it was her father, who then told her to go to bed. In the dim light of thunder during the night, she noticed his red eyes. Hurrying back into her room, she grabbed the notebook again and searched for the source of the medusa's power, coming to know that one of the snakes appeared in a dream of the medusa and made her create the never ending world, parting her from her happiness - her family. Right then, Kano entered her room, wondering what she was doing. Ayano asked him if he would listen to what she has to say and if he could keep it a secret from anyone. Ultimately, she asked for his help, and the two of them started investigating their father's power together. It took them a while to get further with their investigations, long enough for Ayano to become a high school student. Ayano asked him to take on her appearance and go to school for her, so that she could look through Kenjirou's office without raising suspicion.
- They came to know that their father was following a devilish plan to see Ayaka again, who was trapped in the Heat Haze. To accomplish that, they would take the lives of humans in order to have the snakes of the medusa possess them and awaken a new medusa in the real world by gathering the snakes around a queen snake, Kenjirou himself being under the control of one of the snakes. For that purpose, the snake even planned to take the lives of Takane and Haruka, who were to pose as bodies for two other snakes.
- Ayano planned to face the snake and negotiate with it, hoping it would spare the lives of the people she loved. The snake, speaking to her through the body of Kenjirou, however, refused to stop following the wish of Ayano's father to be reunited with his wife. In order to stop her father and the snake from reaching that goal, she decided to enter the Heat Haze and gain a snake herself, without returning into the real world, as it would make it impossible to gather all snakes around the queen. Kano, who arrived at the scene while she was already sitting on the edge of the school roof the three of them were on, tried to talk her out of it. Nevertheless, Ayano jumped off the roof and was swallowed by the Heat Haze, in order to stop people from suffering.