Main •
Uee as Lee Hyo-sim, third sibling, trainer from TS Fitness •
Ha Jun as Kang Tae-ho •
Go Joo-won as Kang Tae-min, heir to Taesan Group
Supporting Hyo-sim's family •
Yoon Mi-ra as Lee Seon-soon, Hyo-sim's mother • Nam Sung-jin as Lee Hyo-seong, Hyo-sim's older brother • Lim Ji-eun as Yang Hee-joo, Hyo-seong's wife • Seo Seol-hwan as Lee Hyo-jun, Hyo-sim's second brother who is preparing for the law exam • Kim Do-yeon as Lee Hyo-do, Hyo-sim's younger brother • Lee Ga-yeon as Ruby, Hyo-seong and Hee-joo's eldest daughter • Lee Joo-won as Lee Phillip, the youngest son of Hyo-seong and Hee-joo
Tae-ho's family • Jeong Young-sook as Choi Myung-hee, Tae-ho's grandmother • Lee Kwang-ki as Yeo Jin-su, executive director of Taesan Group
Uicheon Villa • Jeon Won-ju as Bang Geun-soon, Uicheon Villa building owner whose children and grandchildren immigrated to the United States
TS Fitness • Kang Shin-jo as Yang Jeon-min • Rho Sang-bo as Hwang Chi, a dumb trainer • Lee Ye-sol as Min Ga-young, a trainer •
Jin Tae-hyun as Jang Seon-woo, a trainer • Yoon Ye-in as a talkative old lady who always comes in first at 6 a.m. • Choo Eun-kyung as Kang Jeong-suk • Lee Chun-sik as Hwang No-sik, a grandfather who likes to talk about politics • Park Ki-sun as Choi In-soo, a current orthopedic surgeon • Kim Jong-hoon as Choi Mi-nam, a trainer who causes a commotion at TS Fitness because he couldn't distinguish between public and private affairs
Others •
Nam Bo-ra as Jeong Mi-rim, an aspiring celebrity •
Lim Ju-eun as Choi Sook-yung, daughter of the president and anchor of Korea's best full-length TV live •
Lee Seung-cheol as Chairman Choi, president of TV Live • Ahn Hong-jin as Park Jong-min, a private loan man • Lee Ho-jae as Kang Geun-man, Tae-ho's grandfather, and the first chairman of Taesan Group • Park Hyung-joon as Kang Joon-beom, Tae-ho's father who was so capable during his lifetime that he was likely to be the successor to Taesan, but died in an accident at Daegwallyeong Pass.
Extended • Park Yeo-reum as Han So-ra, a nurse • Kim Mi-ra as Madame Seo, the concubine of Taesan Group's first chairman, Kang Geun-man. ==Production==