Yori is a student of the Yamaguchi Kinja school in Japan whom Ron Stoppable has a crush on. After Kim, she appears to be the most popular of Ron's crushes. In the episode "Exchange," Ron shows repeated interest in Yori, both at their meeting, where he is stunned by her appearance, and again later, when Fukushima is informed that he was right to save a pretty girl. At this time, Ron is not aware that Yori herself has feelings for him. On their second meeting, Ron tells her of his relationship with Kim, which she accepts. Kim shows clear jealousy of Yori, possibly due to Kim believing her to be her greatest competition for Ron's affections.
In her late teens, Yori is a beautiful Japanese school girl, with black hair, tan skin, often wears a black ninja outfit.
Yori was very respectful with everyone she met, the only exception being established villains. Even among people she knew well, she never failed to bow as a sign of respect. She was quite concerned with honor, attempted to behave honorably at all times, and encouraged others to do the same. This is also how she frequently challenged Ron to take the lead role when they were together, and Ron tended to respond to her expectations, both as a way of both proving himself a hero and hopefully impressing Yori as a bonus. Admittedly, most of things that Yori stated would be Ron's honor to do could also have been considered either grunt work, or something a gentleman would be expected to do in a lady's presence (which Ron seemed largely unaware of). Some examples of this included:
- Your honor to carry the bags (Ron brought a huge pile of luggage to the airport and expected someone else to carry them).
- Your honor to walk (all the way up the mountain where the Yamanouchi Ninja School is located, and then back down upon his departure).
- Your honor to go first (when they were about to enter a suspicious and likely dangerous building).
Yori also thought that Ron was very funny with what she called "American style jokes," though in most cases Ron was just uninformed or accident-prone, and was not actually trying to amuse her.
Yori appeared to be a fairly talented ninja, and could usually hold her own in battle unless considerably outnumbered. On the few occasions when they fought, Yori's battles with Kim suggested that they were very evenly matched in skill. In addition, Master Sensei seemed to place a great deal of faith in Yori, which suggested that she was likely either one of his top students, or the most trustworthy.
Yori viewed Master Sensei as a father figure, and obviously cared for and respected him deeply. She was greatly worried for his safety when he was abducted by DNAmy, and upon being reunited with him, rushed to embrace him, before recalling her manners and greeting him with a bow.
Yori was the first person that Ron Stoppable met during his trip to Japan, and served as his guide. They became fast friends, and though Ron was unaware, Yori developed a crush on him. Ron came to see Yori as his "favorite ninja," while Yori came to see Ron as a trusted friend and Yamanouchi's champion. As a result, she would call upon him each time the school was in trouble. Ron didn't realize Yori's true feelings until Kim confirmed them, and the next time they saw each other, Ron and Kim were dating, which Yori did not seem at all bothered by.
Yori's relationship with Kim Possible got off to a rocky start: Kim first met Yori when she abruptly appeared at Middleton High School, and Ron (sworn to secrecy about his time in Japan) came up with a very flimsy lie to explain Yori's presence. Though Yori greeted Kim as a respected comrade, Kim was instantly suspicious of her (aided largely by her own jealousy over the fact that Ron had an attractive female friend that he failed to tell Kim about). Once Ron was allowed to share the secrets of Yamanouchi with Kim, she gradually began to return the respect that Yori had for her from the start. After Kim and Ron began dating, she urged Ron to inform Yori of this. Somewhat surprisingly, Yori approved of Kim and Ron as a couple, adding that she believed Ron was Kim's destiny, and did not seem at all hurt by the announcement.
Yori stated that Hana Stoppable was like a little sister to her. Curiously, they do share similar skin tone and hair color, and Hana's exact biological origin is unknown.
Yori was most often seen wearing "combat clothing" of black shinobi shōzoku, considered the "traditional ninja uniform"; sometimes with hooded mask but generally without. While at the ninja school, especially during practice, she wore a white keikogi, or "practice uniform". On the occasions when Yori needed to appear out in the open as a normal student, she wore a light blue with plaid skirted traditional Japanese serafuku, or "sailor" school uniform.
However, the one thing which Yori always wore was a scarlet red headband.
- Tessen handheld war fans.
- Kusari-fundo or surujin grappling chain.
- Both ninja weapons are identical except one end of the surujin has a spike instead of a second blunt weight, and all we saw was the one end with blunt weight.
- Yori: You must not give up. Even a mighty river was once a stream.
- Ron: But I'm a trickle!
From "Big Bother"
- Ron: Okay! Okay! Yori, the thing is, Kim and I, we're not just friends anymore. We’re kind of, well, dating.
- Yori: I see.
- Ron: Totally didn’t mean to break your heart or anything.
- Yori: I believe my heart is intact.
- Ron: It is? Does everyone have a heart of stone these days?
- Yori: Sensei teaches that change is a part of life, and leads to growth, wisdom, and happiness.
- Yori: I believe Stoppable-san is your destiny, Kim Possible. Like change, we must always welcome destiny.
- Yori bears a striking resemblance to the character Karai from the 2003 incarnation of Teenage Mutant Ninja Turtles.