Youngseo Profile: Ex-ILLIT Finalist To Main Vocalist of ALLDAY PROJECT (2025 Updated)

Youngseo, born Lee Young-seo, is a South Korean singer and the main vocalist and youngest member (maknae) of ALLDAY PROJECT, a co-ed K-pop group formed by The Black Label. With her extensive training background and survival show experience, she brings powerful vocals and maturity well beyond her years.

Biography

• Stage Name: Youngseo (영서)
• Birth Name: Lee Youngseo (이영서)
• Position: Vocalist, Maknae
• Birthday: November 13, 2005
• Blood Type: A
• MBTI: ESTJ
• Foot Size: 250mm
• Zodiac Sign: Scorpio
• Nationality: Korean
• Instagram: @youngseo

Early Life and Pre-Debut Journey

Youngseo was street-cast in front of her school and began her trainee life in the first year of middle school spending four years at Source Music and two years at BELIFT LAB. Under the nickname “Cherry Grapefruit,” she had also been active on YouTube and was a finalist in the 3rd Kids Creator Contest.

Due to her long trainee period, she mentioned having several friends who debuted as idols, among them, she trained the longest with the members of NewJeans.

She gained widespread attention in 2023 when she appeared on JTBC’s survival show “R U Next?” and became a finalist, originally slated to debut with ILLIT.

However, in January 2024, she withdrew from ILLIT prior to their official debut, citing personal and artistic reasons. After leaving BELIFT LAB, there were only rumors that she was practicing as part of a debut group under a certain agency, and no updates were revealed. However, on May 22, 2025, she was seen filming for the first time, leading to speculation that her debut was imminent.

On June 5, 2025, she launched her Instagram account. The next day, on June 6, it was confirmed that she was training under THE BLACK LABEL and preparing to debut in a co-ed group.

Debut and Musical Activities

Youngseo debuted as a main vocalist with ALLDAY PROJECT on June 23, 2025, through the digital single “Famous”. Known for her emotional delivery and vocal strength, she also contributed to the lyrics of “Famous” and “Wicked,” showcasing her involvement beyond just performance.

Her maturity, despite being the youngest in the group, has drawn praise from both fans and professionals in the industry. With a voice that commands attention and a journey marked by perseverance and reinvention, Youngseo stands out as a defining force within ALLDAY PROJECT. Her years of rigorous training, public scrutiny from survival shows, and ultimate debut under The Black Label reflect both resilience and talent. As the youngest member, she brings youthful energy, yet her artistry and vocal ability suggest a maturity far beyond her age.

Personal Life and Public Image

Youngseo is known for her chic and elegant appearance that contrasts with her playful and energetic personality. She is described as detail-oriented, honest, and highly expressive. She studied ballet in her youth and is reportedly friends with members of NewJeans, having trained alongside them.

Despite earlier insecurities about her age during her ILLIT days, she has since emerged with confidence, reflecting on those challenges as part of her growth as an artist. Her favorite color is pink, and she has a fondness for macaroons, cats, and handcrafting beaded accessories.

Facts

• Her life motto is “Let’s make everything fun!”
• Her role model is Billie Eilish.
• Her specialty dish is scrambled eggs. But she spends 98% of her money on food.
• She has large hands and feet, especially her hands, which are so big that other people’s index fingers are the size of her pinky. She’s also very flexible: she can move her ears and do full splits.
• Youngseo shares close friendships with Sakurai Miu of ME:I, Jihyun of 4IREN, and Jeemin of izna.
• The oldest item she owns is a large teddy bear. She believes that all things have value: if she owns something, it’s because it serves a purpose for her. That’s why she collects letters and stickers—because they’re useful in her own way. She doesn’t believe in useless items.
• She sleeps a lot in the mornings and wakes up around 3–4 PM on her days off. The habit she wants to fix is her inability to hear her alarm.
• Although she admits she’s not naturally athletic, her best sport is thigh wrestling.
• She uses a Samsung Galaxy phone.