Hiyori is Zen Kirishimas only daughter who attends primary school at the age of ten to twelve years old. She deeply loves her father and has a good relationship with Takafumi Yokozawa, whom she refers to as "Yokozawa-oniichan" or simply "onii-chan." Although Hiyori had a mother named Sakura, who was Zen's previous wife, she passed away at an early age. It is noted that Hiyori resembles her mother greatly.