Since its premiere in 2013, “The Days," a jukebox musical based on songs by the late Kim Kwang-seok, has had five successful runs, garnering 11 prestigious awards and captivating countless audiences. Throughout this journey, actor Yoo Jun-sang has continued to grace the stage as Jeong-hak, the central character of the musical.

As the musical returns for its sixth run in July, Yoo will share the role of Jeong-hak, a security guard who works at the presidential office, with three other actors: Lee Gun-myung, Oh Man-seok and Um Ki-joon.

Given that Yoon is 53, one might assume he is no longer fit to play the character, whose age is somewhere between 20 and 40. However, Yoo is known for convincingly portraying younger roles and bringing his characters to life.

Achieving this feat did not come without effort and preparation.

In addition to eating less to maintain his weight at 68-69 kilograms, Yoo refuses to remain idle, consistently seeking new ways to stay active.

During his interview with The Korea Herald, Yoo frequently used the word, “endure.”

“In order to endure for a long time, I need to (continue to) work hard. ... When I meet my friend, Choi Jung-won, we encourage each other to endure just a little bit more.” Choi is also a renowned South Korean musical actor.

“After experiencing being recognized by people outside of Korea -- probably because of 'The Uncanny Counter' -- I thought I should endure even harder," he said, referring to the Korean series.

As the interview progressed, it became clear why he uses the term, endure.

For Yoo, enduring means living every moment to the fullest.

He starts the day by doing some type of training each morning -- basic things like writing for more than an hour each morning, like artist Park Dae-sung, an ink-and-wash painting master.

"When I asked why, he explained that since handwriting is essentially drawing, one must write well in order to be able to draw well," Yoo said. Yoo met Park when he was filming the 2016 movie, "The Map Against the World."

"I realized that I need to train in the most fundamental aspects in order to grow as an actor," he added.

He undertakes full runs of the musicals he has previously performed, even in the absence of a clear schedule for future performances of those roles.

For many South Koreans, Yoo is a TV personality who debuted on SBS by winning the broadcaster's 5th TV Actor Contest. However, he has always been drawn to musicals.

Having lived through the times when the musical industry was in its very early stages until today, when the industry accounts for the biggest share in the performing arts, he said he was "glad" that he had "endured."

"Driven by my deep passion for musicals, I chose to return after establishing myself in the realms of broadcasting and film. I am content with this decision and grateful that I never abandoned my love for musicals,” Yoo said.

Yoo has worked on many original productions including "Ben-hur," and he hopes "The Days," which is celebrating its 10th anniversary, can be introduced to a wider audience, including overseas audiences, on stage and in film.

"The music of 'The Days' is just so great and it has great potential to appeal to foreigners," he said, adding that he expects another 10 years in the musical.

Legendary singer-songwriter Kim Kwang-seok's songs are beloved by many Koreans.

Musical fans in South Korea today recognize that original musicals have reached a certain level of excellence, Yoo noted, attributing the source of such growth to audiences.

“Korean audiences give back as much as they receive. They return all the energy we send out. Throughout the years, these qualities have remained unchanged across the generations," he said.

In turn, staff and actors strive not to disappoint the audience.

"I try my best not to disappoint the audience, not even a little. However, there are moments when it becomes inevitable. If they feel disappointed at that moment, it can't be helped, but I still strive to avoid that at all costs," he said.