Sayo is a small child with brown hair and dark brown eyes. She wears a purple dress with a necklace with red beads. She also wears a golden bracelet on her left wrist.
She believes faithfully on her father's dream. We also see that she is extremely smart, as she can understand all of her fathers formulas. After her father left, she took over being the head of the house and caring for Lina. Extremely mature for her age, she is very responsible.
When she was very young, her mother died. Her sister was just a baby. From a young age she had to be the mother of the house taking care of everyone. After her father left, she spent a good amount of time studying her father's notebook, learning the formulas. She and her sister were searching for the secret of creating gems using their father's log. She and her sister went to spa island to look for the last part and end up befriending Luffy and his crew. She was taken hostage by the spa owner to get the secret. Later on she found out that her father did not abandon them.