(SPOILERS AHEAD)
Name: Hiyoko Toukasa
Age: 17
Species: Human
Favourite food: Udon
Likes: Udon, being with her friends, going to tanabata, red meat, competing in physical activities, reading, Pretty Coore
Dislikes: Math, hard school work, a particular doctor partridge bird, seeing Ryouta in a slump, being run over by buffalo while trying to get to school
Homeroom teacher: Kazuaki Nanaki
Classification: Hunter gatherer
Personality in a nutshell: Kind but extremely sporadic and odd
About her (SPOILERS):
Hiyoko is the only human attending St. Pigeonations, a prestigious school for birds. Since she was born birds had been the main species of the world, humans coming at a close second, although she has been told there weren't as many as before. Centuries ago humans were top species, until an attempt at tweaking the bird flu went array.
Her best friend is an average rock dove named Ryouta, a gentle soul with a weak stomach and a sickly Mother. They had been friends since he was chick, since the time Hiyoko found him fallen from his nest and brought him back. It's quite obvious that Ryouta has a crush on his childhood friend, yet Hiyoko is particularly too dense to see it. She finds his crossdressing love odd but still supports it anyhow.
Truthfully, Hiyoko is dense on a whole, being all brawn and no brains. Still, she's easy going and good natured, and puts her heart and soul into everything that she does. She's strong enough to take down herds of buffalo.
On a whole she gets along with her fellow classmates at her school, even such stuffy folks like Sayuka Le Bel. More often than not it is her that has to split up fights between the birds...but, then again, usually that ends with her tossing her classmates haphazardly out the window of the classroom.
Hiyoko lives in a cave, calls herself by a hunter gatherer, and can't start off the day without a little meat in her diet. Her reason for living like this comes from the fact that, unbeknownst to her as she lost her memories of it, her parents were killed eight years before in the Hatoful House incident. Despite not remembering much about them, Hiyoko still wishes to go along with what they were doing: create peace between birds and humans.
She's also the reincarnation of Edel Blau.
In the BBL route of Hatoful Boyfriend (the Bad Boys Love Route, or Hurtful Boyfriend), Hiyoko passes after being poisoned by the Charon Disease lingering in her best friend Ryouta. She is soon cut up, her brain preserved in a scarecrow-like machine, a prototype of a machine that was supposed to replace humans all together. Her spirit still lingers on and keeps Ryouta company.
She also dies twice in the main parts of the game: by Shuu if she tries to go with him, and by the Hawk Party if she gains no romantic relationships with anyone in the school.
Mini info: Her name "Hiyoko" means "chick" in Japanese.
She's often depicted by the fandom as a girl wearing a fake yellow chick head or a rock pigeon head in a futile effort to blend herself in the school full of birds, or as a normal girl with brown shoulder length hair. Moa, Hatoful's creator, has said that Hiyoko's image is up to the fans' imagination.
She has a huge range of special attacks and some are powerful enough to break things.
Her childhood pigeon friend Ryouta is in love with her, but she's too dense to figure it out.
She says and does some of the most epic things in the game.
