Snake of Retaining Eyes/History

Past
Ayano was born to Kenjirou and Ayaka Tateyama.

xx.xx. -5 to 15 Years Before Present
Ayano is present to meet Kano, Kido, and Seto the day they're being taken in by her family, and is the one to disrupt Kido's concealing ability. While the three are talking at her home, she comes into the room asks if they are medusas, angering Kido who slaps her, causing her nose to bleed. Ayano nonetheless warmly reaches out to them, and asks them to be a family with her.

One day, Ayano blindfolds Seto in an attempt to help him with his ability, but he still feels like a monster. Ayano grabs a book and says the color red is used by Tokusatsu heroes on TV, and their red eyes are meant to help people. Ayano then forms the Mekakushi Dan, and Ayaka brings in hoodies to help them hide their eyes and make them look more like a secret society.

While Seto was running away from hearing everyone's thoughts, Ayano was at home, being worried with Kano and Kido. Ayano stops Kido and Kano's arguing and suggests they go out and search for Seto Eventually Seto gets a phone signal and checks his messages, and sees 148 unread messages for Ayano, Kano, and Kido. He then calls them and Kano answers, while Ayano is crying and being consoled by Kido. Ayano snatches the phone from Kano and cries for him to come back home, but Seto's signal is lost. Seto later regains a signal, and his phone goes off from the messages and scares Marry. Ayano meets Marry, along with her family, when Seto brings her home later that day. Marry tells her past to Ayaka and Ayano, and she decides to stay with them. Ayano overhears her mother talking about Azami's diary, saying she doesn't think Marry is human and that she's the descendant of a Medusa. Marry sneaks behind Ayano and asks her where the bathroom is, scaring Ayano without her showing it. Ayaka opens the door, finding Ayano and Marry outside it, and she says that she was just showing Marry to the bathroom.

04.xx. -3 Years
Ayano starts going to high school, while her siblings say they don't feel bad for not being able to.

07.18. -3 Years
She tries to sneak out Azami's diary, but is caught by her mom who talks to her about it, and her mother decides they'll figure this situation out during Summer Break.

08.15. -3 Years
Ayano and Ayaka tell Marry they want to visit her house to learn more about the abilities, and Marry agrees, and Ayaka decides to go on her off day, August 15. Kenjirou, Ayaka, Ayano, and Marry are all driving there when they get caught in a mudslide, killing the first three. While in the Kagerou Daze Ayano was forced to watch Azami's memories over and over before exiting and gaining Favoring Eyes. Once out, Marry runs to her saying her parents are buried and she doesn't know what to do, and Ayano becomes enraged, telling her she should've never met them. At home, Ayano tells Kido, Kano, Seto, and Marry that she thinks Marry should be killed to save them, making Kido slap her. They all leave the house, leaving Ayano alone.

08.16.00
Ayano approaches Hibiya at a park, and introduces herself as "a monster". Hibiya asks if Ayano is one of the "crazies", referring to Mekakushi Dan members, and Ayano says she's not with them at all. Ayano coerces him to try to remember his experience in the Kagerou Daze, but he doesn't want to remember it more. She then says she'll tell him about the other world and uses her eye ability, Favoring Eyes, to show him Azami's history, She takes a short break and tells Hibiya the world is called the Kagerou Daze, and taht's where he and Hiyori went. She then shows Azami giving Marry the Snake of Combining Eyes, and explains the snake abilities to him. Hibiya is then told that she believes Hiyori is already in the real world, to his surprise. Shintaro walks into the conversation, resulting in Ayano's first ever encounter with him.

Ayano, Shintaro, and Hibiya then go to a cafe and Ayano tries to get Shintaro to leave, saying he's an outsider and doesn't have an eye ability. Ayano talks to Shintaro about eye abilities after he says this is important to him, because Momo has an eye ability. Kano then reuintes with Ayano, surprised she's still alive, and figured she'd forgotten about "monsters" like them by now. Kano tells them about Hiyori, thinking Clearing Eyes has possessed her, and tells Ayano that Kido has been killed. Ayano tries to hide her crying, but isn't able to and says this is all her fault. Shintaro, and Momo go to Ayano's home with her, and she decides to tell him about how she died. Momo runs out of the house and Shintaro goes to follow her, and Ayano follows him a little later, after Momo has already been killed by the Snake of Clearing Eyes as Hibiya, who had been possessing him the entire time. Clearing Eyes tells Ayano about his motivations and goals, then Konoha bursts through a window to fight him. This results in Clearing Eyes throwing himself out of another window, which forces Konoha to jump out after him, but is kicked midair wihtout any damage to Hibiya hitting the ground. Clearing Eyes then throws Hibiya in front of a truck, causing him and Konoha to be hit, killing Hibiya and giving Clearing Eyes control of Konoha's body. Ayano leaves and goes to the Dan's hideout with Hiyori to pay respects to Kido, but Kano lets her in. Kano and Ayano talk on the roof about Kido, and express her regret about Marry and cherishes her as part of their family now. They then go downstairs and talk to Seto and Hiyori. Ayano suggests turning Marry into a full Medusa to control Clearing Eyes, but Hiyori says she needs around 3 to make her look like she's become one to trick him.

08.14.00
The Snake of Retaining Eyes has a conversation with Shintaro in the opening of the anime about Shintaro remembering her. She later appears in a dream to Shintaro while he's passed out after the terrorist attack.