From debut to disbanding: Fun facts about HI-BOYZ as TXT’s Yeonjun & Soobin’s Resident Playbook cameo leaves viewers in a frenzy

HI-BOYZ, a fictional band in Resident Playbook, has gained attention with TXT's Soobin and Yeonjun making cameos in the tvN drama. On May 10, 2025, Resident Playbook unveiled episode 9, where Soobin and Yeonjun were shown to be a part of the boy group.

Notably, resident Um Jae-il (played by Kang You-seok) of Yulje Medical Center mentioned that he was a part of the boy group called HI-BOYZ, which was disbanded after releasing one popular song.

In the recent episode, Um Jae-il visited a karaoke place with his fellow residents and performed his song ‘When the Day Comes.’ It was reported earlier that Soobin and Yeonjun would appear on the show as Um Jae-il's fellow bandmates. The two were seen in the music video played on the screen as Um Jae-il performed the song for his friends.

HI-BOYZ has become one of the most talked-about topics among fans of Resident Playbook due to Um Jae-il's warmhearted character, and the TXT members' special appearance added to the excitement.

Here are some facts about the fictional K-pop group HI-BOYZ:

Debut date—February 4, 2011.
First music show nomination—June 2, 2012.
First music show win—June 9, 2012.
Disbandment date—December 28, 2013.
Fandom name—Hello Girls.

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HI-BOYZ' slogan was revealed to be:

Fans: “Hi, My Boys."

Boy group: “Hi, Hello Girls.”

Meanwhile, the revelation of Soobin and Yeonjun as HI-BOYZ members sparked amused reactions from viewers, with comments discussing the "lore" associated with the fictional group.

"No but in all seriousness this is way more funny that an actual acting cameo because the lore this have now... lol," one viewer said.

"they got a music show win and graduated from nugu promoter," another X user commented.

"BEEN SO CONFUSED ABOUT HI BOYZ ALL DAY AND THE WHOLE TIME ITS A FAKE BG FROM RESIDENT PLAYBOOK???," another netizen said.

Viewers discussed the abrupt disbandment of HI-BOYZ and came up with their own theories about it.

"The song has been stuck for the last day in my head…why would they disband such a talented kpop group," one viewer said.

"they disbanded because they sent their two most popular members (yj and sb, obviously) to a survival show for “publicity” but their new group was way more successful and hi-boyz couldn’t recover from their absence," another X user said.

TXT sings HI-BOYZ’ ‘When the Day Comes’ as part of Resident Playbook's original soundtrack

Resident Playbook, starring Go Youn-jung as Oh Yi-young, Kang You-seok as Um Jae-il, Shin Si-ah as Pyo Nam-kyung, and Han Ye-ji as Kim Sa-bi, tells the story of rookie medical professionals in their first year of residency.

tvN unveiled the singer's line-up: I-DLE's Minnie, EXO's D.O., IVE's Ahn Yu-jin, Stray Kids’ Lee Know, I.N., and Seungmin, SEVENTEEN’s DK, aespa's Winter, and TXT for the drama's OST.

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On May 11, TXT dropped the soundtrack ‘When the Day Comes,’ which served as Um Jae-il’s boy group HI-BOYZ’s hit track. The OST has a special meaning, as Soobin and Yeonjun not only lent their voices for the song but also played the role of HI-BOYZ’ members in Resident Playbook.

tvN will also unveil the performance video starring Kang You-seok, Soobin, and Yeonjun, where they will showcase the choreography of the song wearing outfits reminiscent of 2011.

Resident Playbook ep 9 recap: Kim Sa-bi is a Hello Girl

Kim Sa-bi saw Um Jae-il being recognized by a fan in the hospital, who appeared to be shocked. However, during the first year residents’ karaoke session, she was drunk and saw Um Jae-il dance to When the Day Comes. Oh Yi-young and Pyo Nam-kyung hyped up Um Jae-il and were surprised to see Kim Sa-bi joining in to perform the choreography.

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While waiting for the cab, Um Jae-il asked Kim Sa-bi how she hid that she was a Hello Girl, a fan of HI-BOYZ. Kim Sa-bi replied that she was not specifically his fan and that her bias was towards another member named Top Key. Although she denied liking Um Jae-il, she was seen blushing alone in the cab on her way home.

Notably, actors Kang You-seok and Han Ye-ji did a dance challenge on When the Day Comes, which was shared on Stone Entertainment’s social media.

Meanwhile, the When the Day Comes performance video is scheduled to be released on Monday, May 12, 2025, at 12:00 pm KST on Stone Entertainment’s YouTube.

About the author

Inaas is a pop culture writer covering K-drama and K-pop at Sportskeeda. She graduated from the University of Mumbai with a degree in Mass Media, specializing in Journalism. Her love for the Korean entertainment industry started in college and shaped her assignments, eventually leading her to pursue a career as a Korean pop culture writer.

She previously worked as a Community Manager and oversaw more than 50 K-Content creators for an audio app. She has also had the pleasure of interviewing members of famous K-pop groups including BLACKSWAN, UNIS, and actors like Lee Se-young, Um Tae-goo, as part of her ongoing work at Sportskeeda.

Inaas believes in setting aside her biases and verifying news from credible sources when reporting on any topic. She also ensures she takes all the sides of a story into account and crafts holistic articles.

She loves BTS & SEVENTEEN and admires their passion, which continues to inspire her as an individual and a professional. If given a chance to go back in time, she would like to be a part of the famous Korean drama "Reply 1988," since it feels incredibly personal to her due to its portrayal of friendship dynamics.

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Edited by Ameen Fatima