Yasu began her idol training at the start of her 1st junior high year, after attending a Gushiken Academy concert she had dreamed of becoming an idol herself. Yasu's older sister also became a professional idol after graduating high school and teamed up with Momo Fukui, who Yasu admires greatly. She takes after her sister in several ways, including her perfectionism, and often looks to her for both comfort and guidance when her tendencies become overwhelming. She is the head of the festivals stage committee and designs intricate stage sets with the help of her peers. She takes great pride in her creations and anxiously waits on performing idol's feedback before each show.

Although somewhat monotone and calm herself, she adores cute things and has an eye for details that others may not. She formed CiTY MARCH* as an appreciation of aesthetics, the three members having very differing styles. She plans every concert detail meticulously and often stresses over her own performance both before and after lives, a prime example of a perfectionist. Yasu has one sibling, her older sister Ruri, and lives with her parents in Tokyo. Their mother is Swedish and her father is Japanese, and the family often visits Sweden when both sisters have a break; Yasu is even fluent in Swedish!