On the Island
Sun found out she was pregnant using a Widmore Corporation pregnancy test and was shocked, as Jin was sterile before the crash. Jin stated that it was a miracle, but Sun was concerned that the pregnancy was the result of her affair with Jae Lee prior to their time on the Island. ("The Whole Truth")
After the Island
In summer 2005 (presumably in July, 9 months after her conception in October 2004), Sun gave birth to Ji Yeon in Choogdong Hospital in South Korea. Shortly thereafter, Sun and Hurley took Ji Yeon to visit her father's grave. According to Hurley, Ji Yeon looked just like Jin. ("Ji Yeon")
Three years after the rescue of the Oceanic Six, Sun was in London to confront Charles Widmore. Just prior, Sun spoke on the phone with her mother, who was taking care of Ji Yeon. Sun smiled as Ji Yeon said "Mama. Mama." ("There's No Place Like Home, Part 2")
A few days later, when Sun was in Los Angeles, Ji Yeon again spoke to Sun on the telephone. She exclaimed that she missed her mother and wanted her to come back. She was still in her grandmother's care at that time. ("This Place Is Death")
In the afterlife, Sun revealed to Jin that she was pregnant as he carried her, shot and bleeding, away from a restaurant. At the hospital, having an ultrasound with Juliet caused Sun to remember, and seeing Ji Yeon on the ultrasound triggered Jin's own awakening. Together, they remembered their previous lives. ("The End")
- Out of all the main characters, she has only met Sun and Hurley.
- Ji Yeon means "flower of wisdom." ("Ji Yeon-Enhanced")
- Ji Yeon is an orphan, surviving both her parents.
- Ji Yeon is one of eight characters to have their name appear in the title of an episode, the others being Sun, Hurley, Locke, Kate, Dave, Tricia Tanaka, and Sawyer (as LaFleur). ("Ji Yeon")
- Yunjin Kim played a character named Ji Yeon Yu in the Korean thriller Seven Days.
- The titles of three episodes refer to Ji Yeon, but indirectly: "The Whole Truth", which refers to Sun's pregnancy, "D.O.C.", which refers to the date of Ji Yeon's conception, and, of course, "Ji Yeon".
- The actress who plays Ji Yeon, Jaymie Kim, has the surname Kim, the same surname as the actors who play her parents, Daniel Dae Kim, Yunjin Kim, and Sophie Kim, who plays a young Sun in "The Glass Ballerina".
- She is one of three non-main characters to have their name in an episode title. The others are Dave and Tricia Tanaka.