She is half-human, half-toriningen (a race of beautiful bird people).
Hiyowa is very pessimistic and is timid and fearful of others. The only person she fully trusts is her older half-brother, Mamoru.
She has mild photophobia.
Aside from her precious handmade ragdoll, Stuffy, Hiyowa only has the tattered rags she is garbed in.
Hiyowa is the daughter of Washi Tatakinomeshi, but she is horribly treated by her father. Her human mother died giving birth to her, which is why she is hated by her father. Hiyowa was kept chained to the floor of her father's basement and had been there almost her entire life.
Hiyowa's father beat her horribly on a regular basis, treating her little better than an old punching bag. Until her recent escape, all she was given to eat were leftover scraps.