Eunseo

Eunseo is a South Korean singer, dancer, and one of the ten members of WJSN (Cosmic Girls), the space-concept K-pop girl group under Starship Entertainment. Born Son Ju-yeon on May 27, 1998, in Incheon, South Korea, Eunseo has spent a decade winning fans over with her sharp, clean dance lines, sub-vocal work, and famously bright, sunshine-like personality — a trait that earned her the nickname “Sunlight Girl” within the group’s fandom, Ujung.

From Trainee to Cosmic Girl

Before she ever stepped on a WJSN stage, Eunseo put in years of quiet groundwork. She first joined Pledis Entertainment as a trainee in 2011, competing at the agency’s “Happy Pledis” evaluations, but she eventually left to look for a better fit. She found it at Starship Entertainment, where she trained for roughly three years, sharpening her dancing and vocals alongside labelmates. During this pre-debut stretch, she even popped up in Monsta X‘s “Rush” music video, a small preview of the stage presence she’d soon bring to her own group.

On December 17, 2015, Starship revealed her as part of WJSN’s Joy Unit, alongside Xuan Yi and Yeoreum. Two months later, on February 25, 2016, she officially debuted with the full group’s first mini album, Would You Like?, led by the single “Mo Mo Mo.”

Growing With WJSN

As WJSN built its discography through the late 2010s, Eunseo grew into her role as the group’s lead dancer and sub-vocalist. In August 2016, she joined the Starship project unit Y-Teen, teaming up with Monsta X for a run of singles and CF campaigns. Her athleticism and work ethic became a running theme in her idol career — she’s often cited as the fastest runner in WJSN and once earned a bronze medal at the Idol Star Athletics Championships (ISAC). In 2018, she appeared on the military-style variety show “Real Men 300,” where she stood out as the only female recruit able to complete a full set of push-ups.

Eunseo also branched into acting during this period, taking on small screen roles including a part in the JTBC drama “Idol: The Coup.” In May 2021, she debuted in WJSN’s second official subunit, WJSN THE BLACK, releasing the single album “My Attitude” alongside Seola, Bona, and Exy — a moodier, more mature concept that let her show off a different side of her artistry.

Personality and Personal Life

Ask any longtime Ujung (WJSN’s fandom) about Eunseo, and they’ll usually mention her warmth first. She’s the youngest of three daughters, has two older sisters, and is often called the “dad” of the WJSN dorm for her steady, caretaking energy. She can play piano, guitar, drums, and tambourine, and she and member Dayoung are widely considered the best cooks in the group. Fittingly for her ENFJ personality type, she thrives around people but admits multitasking isn’t her strong suit — when she focuses on something, she focuses all the way in.

In March 2023, when WJSN’s Chinese members departed the group, Eunseo was among the members who renewed her exclusive contract with Starship Entertainment, keeping WJSN together as a ten-member act. She studied Acting Arts at Sungkyunkwan University, rounding out her performance skills beyond the stage.

Eunseo at a Glance

More than ten years into her career, Eunseo remains one of WJSN‘s most dependable performers — the member fans point to when they talk about the group’s dance line, its work ethic, and its enduring, sunny chemistry.