The year he turned 17, he debuted in the seven-member group BTOB. In 2013, he appeared in tvN’s Reply 1994 as Ssuk-ssuk; the drama ended that December. In 2014, he played Kang Min-gu in tvN’s Plus Nine Boys and sang on its soundtrack.
The breakthrough yearThe year he turned 20, he played Gong Tae-kwang in KBS2’s Who Are You: School 2015, and became known through the drama. That year he also appeared on King of Mask Singer, We Got Married 4 and SBS’s The Village: Achiara’s Secret.
In 2016, he released music with the unit BTOB-Blue, and in December he appeared in tvN’s Guardian: The Lonely and Great God as Yoo Deok-hwa. In 2017, he won the Rising Star Award at the Korea Cable TV Awards for Guardian: The Lonely and Great God, and in October BTOB released its second studio album Brother Act. On Dec. 31, he began appearing on SBS’s Master in the House.
In December 2018, he won the Excellence Award in Variety at the SBS Entertainment Awards for Master in the House. In December 2019, he released a project single and won awards in two categories at the SBS Entertainment Awards.
In May 2020, he enlisted for active duty, and JTBC’s Mystic Pop-up Bar first aired the same month. He was discharged in November 2021 and appeared on Master in the House again in December.
In 2022, he returned after his discharge with MBC’s The Golden Spoon. In December 2023, he signed an exclusive contract with the production company iWill Media. In November 2024, he appeared in the Netflix variety show Zombieverse: New Blood.
In 2025, he played Yoon Gap in SBS’s The Haunted Palace, which ended in June. In July 2026, he appeared in a video letter on tvN’s 10th anniversary special for Guardian: The Lonely and Great God.
Yook Sung-jae debuted in the group BTOB on Mar 21, 2012, the year he turned 17, and became known in 2015, the year he turned 20, for playing Gong Tae-kwang in KBS2’s Who Are You: School 2015. In 2016, he appeared in Guardian: The Lonely and Great God as Yoo Deok-hwa.
Ages are by calendar year (the year minus the birth year), birthdays aside.
Debuted in the seven-member group BTOB with Seo Eun-kwang, Lee Min-hyuk, Lee Chang-sub, Im Hyun-sik, Peniel and Jung Il-hoon. The group held its debut showcase at the JW Marriott Hotel in Banpo-dong, Seoul.
Source 01 · Maeil Business Newspaper (Korean) · BTOB debut showcase · opens in a new tabAppeared as Ssuk-ssuk, the youngest son of the characters played by Sung Dong-il and Lee Il-hwa. The final episode aired on this date.
Source 02 · OSEN (Korean) · Reply 1994 Ssuk-ssuk · opens in a new tab The date is the finale’s air date. The first broadcast date was not confirmed.Played Kang Min-gu in the tvN Friday-Saturday drama Plus Nine Boys, and sang “Curious,” the theme song for the drama’s on-screen couple.
Source 03 · Etoday (Korean) · Plus Nine Boys OST · opens in a new tabAppeared as Gong Tae-kwang alongside Kim So-hyun and Nam Joo-hyuk. The drama ended on June 16.
Talked about what changed after appearing masked on King of Mask Singer under the name “I’m Tired Now, Ttaeng-beol.”
Source 10 · TV Daily (Korean) · Radio Star with Yook Sung-jae · opens in a new tab The King of Mask Singer broadcast date was not confirmed.Appeared with Joy of Red Velvet as the new virtual married couple.
Source 11 · OSEN (Korean) · We Got Married 4 Yook Sung-jae and Joy · opens in a new tabAppeared as Park Woo-jae, a character in a police uniform.
Source 12 · News1 (Korean) · The Village: Achiara’s Secret · opens in a new tabFormed BTOB-Blue, the group’s first vocal-line unit, with Seo Eun-kwang, Lee Chang-sub and Im Hyun-sik, and released a digital single.
Source 13 · Newspim (Korean) · BTOB-Blue formed · opens in a new tabAppeared as Yoo Deok-hwa, a third-generation chaebol heir. The drama began with episode 1 on this date.
Source 14 · Sports Chosun (Korean) · Candle messages in Guardian: The Lonely and Great God · opens in a new tabSource 15 · Ilyo Seoul (Korean) · Korea Cable TV Awards · opens in a new tabSource 07 · Herald Muse (Korean) · BTOB members’ individual activities · opens in a new tabGuardian: The Lonely and Great God won four awards at the ceremony, and Yook Sung-jae received the Rising Star Award.
Source 15 · Ilyo Seoul (Korean) · Korea Cable TV Awards · opens in a new tab The ceremony date was not confirmed. Based on an article dated Mar. 18, 2017.The title track “Missing You” was written by member Im Hyun-sik. The group held a release press conference at the Imperial Palace Seoul.
Source 24 · Edaily (Korean) · BTOB second album Brother Act · opens in a new tabAppeared with Lee Seung-gi, Lee Sang-yoon and Yang Se-hyung. The first master was the rock singer Jeon In-kwon.
Source 16 · Newsen (Korean) · Master in the House first broadcast · opens in a new tabReceived the Excellence Award in the variety category for Master in the House.
Source 25 · News1 (Korean) · 2018 SBS Entertainment Awards, Excellence Award in Variety · opens in a new tabReleased a project single.
Source 17 · Sports Donga (Korean) · 2019 SBS Entertainment Awards · opens in a new tabReceived awards in two categories for appearing on Master in the House.
Source 17 · Sports Donga (Korean) · 2019 SBS Entertainment Awards · opens in a new tabEnlisted on the same day as BTOB’s Im Hyun-sik and Pentagon’s Jinho.
Source 18 · Sports Donga (Korean) · Yook Sung-jae, Im Hyun-sik and Jinho enlist · opens in a new tabAppeared as Han Kang-bae alongside Hwang Jung-eum and Choi Won-young.
Source 26 · Ilgan Sports (Korean) · Mystic Pop-up Bar first broadcast · opens in a new tabServed on active duty and was discharged.
Source 19 · TenAsia (Korean) · Master in the House after discharge · opens in a new tabAppeared on Master in the House as its youngest member for a day, his first variety show after discharge.
Source 19 · TenAsia (Korean) · Master in the House after discharge · opens in a new tabAppeared in the drama, his comeback project after his discharge. Episode 1 drew a 5.4% rating (Nielsen Korea, nationwide).
Source 20 · JTBC (Korean) · The Golden Spoon first broadcast · opens in a new tabSigned an exclusive contract with the production company iWill Media. iWill Media said it would also support BTOB’s activities.
Source 21 · Maeil Business Newspaper (Korean) · Exclusive contract with iWill Media · opens in a new tabAppeared in the Netflix variety show Zombieverse: New Blood, which was first released at 5 p.m. that day.
Source 27 · Sports Kyunghyang (Korean) · Zombieverse: New Blood cast · opens in a new tabIn the Friday-Saturday drama The Haunted Palace, played a dual role as Yoon Gap, a royal librarian possessed by the evil imugi spirit Gangcheori.
Source 22 · YTN (Korean) · The Haunted Palace finale comments · opens in a new tabAppeared in a video letter as the actor who played Yoo Deok-hwa, and said the drama might return for a second season.
Source 23 · MK Sports (Korean) · Guardian: The Lonely and Great God 10th anniversary · opens in a new tabEND OF SELECTED RECORDSSelected records, 2012–2026 · not a complete list of work. “Key moment” is an editorial label, not a measure of success.
What did they do, and at what age?
AgeTrail lines up the key moments of a life by age.
Debut and breakthrough are marked separately, and every record has a source.
Music · South Korea
May 2, 1995 —
Ages are counted from the birth year 1995: the year of the event minus 1995, birthdays aside. “Key moment” labels and the connecting story are AgeTrail's editorial reading.
Fact-checked: 2026.10.06 · An independent archive, not affiliated with the person or their agency.