Saori, nicknamed Saorin (さおりん), is a girl who is a fifth grader in Shuichi's class at the beginning of Wandering Son. She takes an interest in encouraging Shuichi to dress as the correct gender of a teenage girl, even going so far as to buy Shuichi an expensive dress for Shuichi's birthday, which Shuichi later returns, much to her displeasure. Saori finds it difficult to associate with others; she has few friends, though she becomes close to Shuichi. She tends to convey what is on her mind and disregards how others may take what she says. As Saori grows up, she gradually becomes more standoffish and stoic; she even develops bad relations with her teachers. Despite her self-centered attitude, she remains popular among her male classmates due to her cute, pretty physical attractiveness, especially wearing her hair in twin tails. She is a sensitive girl whose temper sometimes gets the better of her when reprimanding bullies that tease Shuichi, because of Shuichi's femininity and effeminate mannerisms. Saori is often emotionally affected by circumstances involving Shuichi, because of her deep, hidden feelings for Shuichi. Saori converts to Christianity, partly because of her desire to seek forgiveness for her previous actions, though she only attends the religious services when feeling guilty about her behavior.
Saori is shown to be very anti-social and seemingly cold to even her closest friends, often ignoring them or saying hurtful things about them. But this is, in fact, a façade, as she is actually secretly caring towards her friends. However, due to an incident before entering middle school; that event has caused her to become distant and hateful. She is in fact very protective of Shuichi, and is affected by many things surrounding him, evident by the fact that she stopped going to school upon hearing Shuichi had begun dating Anna Suehiro.
Saori was one of the original people who saw the potential of how cute Shuichi is dressing up as a girl, and often offered encouragment to do so. As such, she is very accepting of this and wants Shuichi to continue to dress as their correct gender identity as long as the desire is there.
She is first introduced as friends of Yoshino Takatsuki & Nitori Shuuichi, but due to a falling out before middle school, that has caused the friends to become distant towards each other, with Saori becoming hateful towards Yoshino. Saori's sometimes jealousy becomes clear when someone in the class teases Shuichi about having dated Yoshino the year before, which Saori proceeds to come from behind and hit the person over the head with a book, knocking them to the floor, and then promptly leaving the classroom.
It is later shown that the reason they had a falling out was because Saori confessed her love towards Shuichi, which was turned down, she then finds out that Shuichi had earlier confessed love for Yoshino, which that was turned down. This causes a rift between the friends, Saori stating that she hates Yoshino, which in turn causes Yoshino to say that they, in fact, reciprocally hates Saori, because of her victim mentality.
Kanako Sasa becomes the mediator mainly between Yoshino and Saori, trying to get them to forgive and forget the past, but to no avail. But throughout the story Yoshino and Saori gradually begin to mend their old wounds, especially when it is revealed that Shuichi and Anna Suehiro have begun dating, which crushes Saori, causing her to abandon school. Yoshino brings her homework to her home, and tries to rally her to keep going to school and to not let such things ruin her future.
One weekend, during the high school year, Saori invites Shuichi to her bedroom, where she has an extensive collection of pretty dresses laid out on her bed. She invites Shuichi to try them on, one by one, so as to discern the best female fashion style for Shuichi. While Shuichi is sitting in front of a makeup mirror, wearing a very attractive dress, Saori places a hair extension on Shuichi, brushes their hair, and then confesses to Shuichi that they have always been a very special person to her. A special girl-with-girl bonding then takes place between them.
Eventually Saori is able to forgive Yoshino and responds to Yoshino's comment on "everyone being special", Saori feeling that there really is no meaning in saying everyone is special, but Yoshio says that, just because that is just the way ze is.