Sayo has slanted green eyes and long, light, teal hair about navel length with her forelocks worn behind the ear with a curl on the end. Her bangs are neatly parted with the exception of a single loose lock.
Her casual attire is simple with a tomboyish, yet cute tone, mixing pale and dark shades.
A serious and fussy girl, Sayo is somewhat cold in nature, even towards those she is close to. She never cuts corners or accepts shoddy workmanship, and is far too serious for her own good. She tends to stubbornly deny liking or being fond of certain things, such as fluffy animals or french fries.
In comparison to her sister Hina, Sayo is fairly stiff and sharp, and is highly stubborn when trying to do what she believes is best for others. She is very formal, and address most people by their last names. Like Yukina, she is prone to make snide or rude remarks, though often these remarks do not reflect how she actually feels.
Sayo has a severe inferiority complex, originating from her relationship with her talented 'younger' twin sister. Whereas Hina can master new skills with ease, Sayo requires a great deal of information before she can even begin to practice. Although Sayo and Hina were originally very close, this feeling of inadequacy caused Sayo to drift away from her twin, until eventually she began trying to shut her out of her life entirely.
Sayo began to play the guitar in part because it was something her sister wasn't already doing. To ensure that she would have at least one thing to feel proud of, even if Hina started playing as well, she focused entirely on mastering the technical aspects of playing the guitar, as opposed to musicality. However, despite her efforts, when Hina began playing the guitar she was able to surpass Sayo's considerable head-start with ease. Although Hina was, indeed, not quite as technically skilled as Sayo, her music had a personality to it that, in Sayo's view, made it far more enjoyable to listen to. This revelation left Sayo feeling miserable and listless, and nearly caused her to quit playing guitar entirely.
Her anxieties also apply more generally, to her role within the band and to activities outside of it. Although her guitar playing is frequently praised by other members of Roselia, especially Ako, and by her sister, Sayo describes the sound of her guitar as "lifeless." Although she is still focused on precision, hearing her sister's music has made her realize that technical skill alone is not enough to create good music, and that if she ever wants to catch up to Hina, she'll have to find a unique sound of her own.
A list of characters Sayo interacts with in the game.
- ESP Guitars will release a real-life version of Sayo's guitar, M-II (Full Name: M-II Roselia Sayo), alongside Lisa's bass, and other Bandori merchandise relating to Roselia.
- She is the tallest Roselia member.
- She is a member of the Archery (Kyudo) Club and Disciplinary Committee.
- Sayo loves reading music magazines and in one in-game conversation, was even shown carrying seven of them in her school bag.