For most of his career, Yeo Jin-goo has played the younger versions of characters.

He acted out the childhood of a Robin Hood-esque hero in the 2008 TV series “Iljimae.” He played a youngster who grows up to be a gambler in the crime film “Tazza: The High Rollers.” His character in the TV drama “Giant” later became the charismatic founder of a building company. In 2012, he stole viewers’ hearts with the younger role of a Joseon-era king in the period series “Moon Embracing the Sun.”

Although many child actors feel pressured as they grow older to veer away from that image of perennial innocence emblazoned in viewers’ minds, Yeo says he is at ease with public perception.

“For me, I hope viewers look back on the different roles I’ve done,” said Yeo, now 20 years old, at an interview in Samcheong-dong, Seoul on Tuesday. “I hope they can look back and reminisce. It’s not too pressuring. I think viewers will naturally come to accept (my growth).”

With his deep voice and intense stare, Yeo had a reputation as a heartthrob in Korean TV and film long before his transition into adulthood. He earned the nickname “oppa,” a Korean term used when women affectionately refer to older males. But that mature image did not burden him, Yeo said.

“I like the nickname,” he said. “It’s fun. I hope I can keep hearing it. But I’m a lot more fun than people think.”

Yeo’s latest film is another period flick, “Warriors of the Dawn,” which opens in Korean theaters on May 31. Yeo plays Gwanghaegun, the bookish, timid heir to the Joseon throne left to deal with the danger of the Japanese invasion of Korea in 1592.

The film, distributed by Fox International Productions Korea, has been sold internationally and will open in North America on June 16.

“He is the king’s heir but he doesn’t seem like an heir,” Yeo said of his role.

Yeo’s Gwanghaegun is a struggling adolescent who has no idea how to govern a country. “But later, as he earns the trust (of the people), he comes to discover empathy for his people that even he did not know he had.”

Yeo had focused on the “explosive expression” of emotions in his past works -- especially in the 2013 fantasy thriller “Hwayi: A Monster Boy” where he played a young criminal. But the actor opted for a more subtle delivery this time, he said.

“I wanted a performance that was like a softly running stream,” he said. “Like a piece of silk that is waving. ... I wanted to show that inner change that (Gwanghaegun) himself experiences for the first time.”

Yeo is currently taking time off from his studies at the Chung-Ang University School of Theater.

“It just wasn’t possible with my schedule,” said Yeo, who is currently starring in the sci-fi TV series “Circle.” “It would’ve been harmful to myself, the professors and my fellow students.”

At school, he is no different from his peers, Yeo said.

“I’ve always acted with older (actors). ... My peers at school had a different color of energy. I have so many thoughts and keep trying to become calmer. But their passion was surprising. It moved me.”

Despite 12 years of on-set experience, it was Yeo’s first time studying theater in college.

“I get told off a lot,” he said, laughing. “Theater is completely different (from TV and film).”

Still young and eager, Yeo said he hoped to become “a more versatile actor” in his later years.

By Rumy Doo (doo@heraldcorp.com)