Yi is a teenager who lives in Shanghai with her mother and her severe grandmother. Since the loss of her father, she likes to go to her fort and play her violin, which is all that remains of him, promising to fulfill her promise that she will go on a trip. One night Yi notices a yeti on her rooftop. The yeti, whom he calls Everest, is on the run from the ruthless Dr. Zara, a mad scientist and poacher who tries to sell Everest to the highest bidder. Now, it's up to Yi, aided by her friends Ping and Jin, to help Everest find her way home.
Yi is a 15 years old Chinese girl who plays the violin and lives with her mom and grandmother. Yi is very anti-social and work-alcoholic as she prefers getting work done instead of having fun if necessary. This is a result of her father's death where she cuts herself off from her family and friends and works numerous jobs to earn money just so she can go traveling like her dad wanted her to do before he died, an example is peng wanting to play with Yi but she couldn't. Despite this, Yi does have a good heart. When she meets Everest and realizes he's friendly, Yi helps Everest by hiding him from his pursuers, treats his wound, and feeds him dumplings. She even decided to help Everest get back to home without any hesitation.
Throughout the journey, Yi lets out her feelings over her father's death which she never done before and slowly starts to reconcile with her friends, especially Jin who Yi was most estranged to because of the latter's popularity and the death of her father. She also realizes how much family and friends are important and that they should be a part of life, while not letting heartache overtake you.
Yi also proves to be very forgiving as she quickly forgives Everest when he repaired her dad's violin after he accidentally broke it and later to Burnish who spent most of the time trying to capture Everest until realizing his mistakes. Yi is also intelligent as she comes up with ideas during the adventure take Everest home and avoid Burnish, Dr. Zara, and their minions. Yi is also very determined and brave as she committed herself to returning Everest to his family and stopping Dr. Zara from using Everest for profit.
During and after the adventure, Yi learns and becomes more social and open towards people, including her family and friends, and finally comes to terms with her sorrow over her father's death.
She is the fifth leading female protagonist in a Dreamworks Animation film, after Ginormica from Monsters vs. Aliens, Eep Crood from The Croods, Ginger from Chicken Run and Poppy, from Trolls. She is also the second protagonist from China, after Po the kung fu panda Dragon Warrior, from Kung Fu Panda
Given the similarities between the three movies, Yi fills in this movie the role that Percy filled in Smallfoot and Sir Lional Frost filled in Missing Link.
The name "Yi" means 'happy' in Chinese.
In the Hebrew dub of the film, however, she is referred to as Li (or Lee) instead of Yi.