Hiyoko was born as the heiress to the Saionji Clan, the head of the school of traditional Japanese dance, and her traditionalist family was very overbearing due to this important role. Making things worse, her chosen bloodline was constantly targeted by conspiracies and assassinations due to jealous people. As a child, she constantly suffered cruel and even life-threatening pranks and threats, like having pins in her shoes, dead mice scattered all over her bed, and poisoned food.
She originally lived with her parents and she loved her father, who was different from her other family due to only being related to the family through marriage. He was very protective of Hiyoko, always staying by her side and happily watching her dancing. However, he had a very low rank in the family, and Hiyoko wished she could protect him from becoming the head of the family.
Soon, Hiyoko was taken from her parents by her grandmother, who wanted to raise her strictly according to the family traditions for the sake of the Clan's pride. She didn't even let Hiyoko see her parents, supposedly considering her father to be a bad influence on her. While considering her a hag, Hiyoko was grateful to her grandmother for raising her and taking good care of her.
Because of Hiyoko's past, she considers herself part of the noble class and everybody else meager slaves. Hiyoko is said to be a rookie dancer, but it is said that her family has high expectations as she has done many shows overseas. She is also popular with younger audiences, though most of her fans are older males.
She previously attended Golden Light Girl's Institute before enrolling into Hope's Peak Academy. It's heavily implied that she never had any friends due to growing a mean and distrustful personality in order to defend herself in the past.
While in Hope's Peak Academy, Hiyoko befriended Mahiru, Ibuki, Mikan, and Sato. During their time together, they discovered a corpse in the music room. This was later revealed to be Fuyuhiko Kuzuryu's sister, who was murdered by Sato. A few days later, Sato was killed by Fuyuhiko. When Mikan, who was late, asks what's wrong, Hiyoko suggests her to enter the classroom. This part of Hiyoko's life was revealed in Monokuma's second motive, "Twilight Syndrome Murder Case".
