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

HI-BOYZ, a fictional band in Resident Playbook, gains attention as TXT's Soobin and Yeonjun make 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 had mentioned that he was a part of the boy group called HI-BOYZ, which faced disbandment after releasing one popular song.

In the recent episode, Um Jae-il visited a karaoke with his fellow residents and performed his song ‘When the Day Comes.’ Previously, it was reported that Soobin and Yeonjun will 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 Un Jae-il's warmhearted character, and adding to the excitement was the TXT members' special appearance.

Here are some of the important 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.

HI-BOYZ' slogan was revealed to be:

Fans: “Hi, My Boys."

Boy group: “Hi, Hello Girls.”

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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.

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 brings 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 exuding 2011 vibes.

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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 and 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 shocked to see that Kim Sa-bi also joined him to perform the choreography.

While waiting for the cab, Um Jae-il asked Kim Sa-bi how she hid that she was a Hello Girl, HI-BOYZ's fan. Kim Sa-bi replied that she was not specifically his fan and her bias was 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.