Ako was a small child who had short brown hair with two side pigtails held with yellow bobbles and brown eyes.
As "livestock", she wore a dark choker with a tag and a sleeveless one piece dress with a hood. The dress had a design on the eyelet and black lining. She wore dark wrist bands on her both hands, and like the rest of the children, Ako didn't wear any footwear.
Anime: Livestock wear shoes in the anime.
Ako seemed to be a happy and cheerful girl in her interaction with others. She also noticed that Yu was not eating and asked why and cheerfully announced that she also wanted a birthday when Taichi mimicked Kōta's announcement that today was his.
At some point in her life, her parents abandoned her at the Hyakuya Orphanage which was run by the Brotherhood of a Thousand Nights, a religious organization infamous for its cruel experimentation on orphans.
Events of 2016
Shortly after Yu's arrival at the orphanage, the director suddenly began to bleed from her nose and mouth and collapsed to the ground.
The adults perished, Third Progenitor Krul Tepes led the vampire invasion on Tokyo. For the next four years, the orphans survived as livestock for the vampires in the vampire capital of Sanguinem, which is located under Kyoto.
She is happy to see Yu return to their home in the vampire city, and shares the news of what Akane is preparing. On their way out of Sanguinem she is in awe of the view of the city and asks Mika where are they going, and why they will be saying goodbye to this world.
Arriving at the exit, it is revealed as a trap by Ferid Bathory who begins his murder of the orphans by draining Ako of her blood first.
Four years later she is remembered by Yu when his path is blocked by Ferid and he remembers him murdering his family. Ako is also visualized when Kureto is reading Yu's background and how his family were killed during their getaway attempt.
When Mika is being defended by Shinoa, Yoichi, Kimizuki and Mitsuba, he thinks how they are defending him because they know he is Yu's family. Ako is visualized playing football with the other orphans where they were inviting him to play as well.
Her older family member in the Hyakuya Orphanage, Ako was holding Mika's hand being part of the first people to introduce themselves to Yu, smiling as they did so. She listens as Yu explains his background to them including the loss of his parents, and watches inquisitively to see whether Yu would accept Mika's offer of friendship. Living together in a place in Sanguinem, Ako is pleased to see that Yu has returned home going to the door to greet him. She excitedly shares details of a big surprise in the kitchen. When eating the surprise curry, Ako notices and asks why Yu is not eating anything, asking if he is not hungry. When leaving Sanguinem she holds onto Yu's arm when Ferid appears.
She holds Mika's hand as she joins him in introducing himself to Yu when he first arrived at the orphanage. In Sanguinem, when Taichi asks why Mika is not there for dinner, Ako asks if he does not like curry. On the way out of the city she asks Mika where are they going.
Having lived together at the orphanage, Ako joins Fumie in greeting Yu at the door when he arrives back in their new home in Sanguinem.
A boy appearing more similar in age to herself, they lived together in Sanguinem where they both greeted Yu home. They sat beside one another when eating and like the rest of their family they were close.
Ako was with Kōta and Mika as the first orphans to introduce themselves to Yu when he arrived at the orphanage. In the sleeping quarters in Sanguinem they were beside one another.
Ako comes across him when she tries to leave Sanguinem and is the first to be murdered by the vampire noble in a trap where he drains her of her blood.
- The name Ako means "second, Asia" (亜) (a) and "child" (子) (ko).
- Ako's surname Hyakuya means "hundred" (百) (hyaku) and "night" (夜) (ya).
- Once the Hyakuya family wanted escape from the vampire city, Ako was the first orphan who was killed by Ferid Bathory.
- After Mikaela Hyakuya, Ako was the second orphan of her family to have their blood sucked by Ferid.