|“||I don't give a damn. Friendship isn't real anyway. But how long would you last as my enemy?||„|
|~ Jen Yu to Yu Shu Lien|
Jen Yu first appears as the docile debutante who meets and soon becomes friendly with Yu Shu Lien, whom she idolizes as a skillful female warrior who lives by her own rules.
It is later revealed however, that Jen is the apprentice of the murderous Jade Fox posing as a governess, and steals the Green Destiny sword for herself, though she later returns it. It is around this time that Jade Fox realizes that Jen Yu has been secretly reading and studying the stolen Wudang manual (which the illiterate Jade Fox could not do) and as a consequence has now surpassed her skills.
Jen Yu is also revealed to be in a relationship with a thief she encountered in the Silk Road named Lo. Although she has fallen in love with him, Jen Yu now believes they cannot be together due to her status as an aristocrat.
The Invincible Sword Goddess
Despairing due to feelings of isolation, Jen Yu steals the Green Destiny once again and runs away, intending to live a life of adventure as an arrogant and confrontational tomboy. With the Green Destiny in hand, no warrior is a match for her, as she can simply destroy their weapons. Yu Shu Lien and Li Mu Bai track her down, but Jen Yu has no intentions of relinquishing the Green Destiny or allowing Li Mu Bai to take her under his wing.
When Yu Shu Lien points out how selfish and insensitive Jen Yu is being, having shown those who are trying to help her nothing but contempt and indifference, Jen Yu declares her to be an enemy, leading to a fight between the two. As was the case before, Jen Yu is able to get the upper hand simply by destroying any weapon raised against her using the Green Destiny. However, Yu Shu Lien manages to use the sword's invincibility against Jen Yu, ultimately winning the duel. Yu Shu Lien hesitates with her sword at Jen Yu's throat, unable to bring herself to kill her. Jen Yu, bitter at having been defeated, takes advantage of Yu Shu Lien's mercy and cuts her across the arm. Li Mu Bai arrives to witness Jen Yu's shameful act, and pursues her into the forest as she tries to escape.
After a chase through the tree-tops of a bamboo forest, he takes the Green Destiny from her. Li Mu Bai tries to get Jen Yu to come with him and become his student, as he still recognizes her potential, but she refuses and instead dives into the river to chase after the Green Destiny as Li Mu Bai throws it away. Jade Fox, who has been watching, snatches Jen Yu while she floats unconscious in the water.
Jade Fox, now embittered for Jen Yu surpassing her as a warrior, drugs her and uses her as bait for her sworn enemy, Li Mu Bai. As he enters the cave where Jen lies frail and sick, Jade Fox shoots poisoned darts and Li Mu Bai is hit before he is able to kill Jade Fox. As she dies, Jade Fox admits that she was aiming for Jen Yu as she spitefully condemns her as being the "true poison". Now remorseful, Jen Yu tries to get Li Mu Bai the antidote he needs, but he expires before she can bring it back to him in time.
Yu Shu Lien urges Jen Yu to be true to herself no matter what she does in life. Going to the Wudang, she is reunited with Lo, but the morning after a night of passion she goes to the edge of the mountain, overlooking the clouds. Earlier, Lo had told her a story of a man who had a wish fulfilled by leaping off the edge into the clouds. Jen Yu asks Lo to make a wish of his own, to which he asks that they go back to the desert together. As Jen Yu leaps into the clouds, Lo smiles.