South Korean singer Lee Chan-hyuk quietly joined the Korean marines this week.

The 21-year-old Akdong Musician singer will fulfill his mandatory two-year military service with the Republic of Korea Marine Corps, according to The Chosun Ilbo.

Lee's agency, YG Entertainment, said the K-pop star entered boot camp Monday in Pohang, South Korea. He will complete six weeks of basic training before he is assigned to a unit.

"We gave him a quiet send-off, in accordance with his wishes," the agency said.

Lee's sister, Lee Su-hyun, performs with him as Akdong Musician. The Korea Times reported Lee's parents, a few close friends and YG Entertainment staff saw the singer off at the training center.

Many K-pop stars postpone their military service until their late 20s or 30s. Lee explained he enlisted now to train with others his age and "to build diverse experiences and improve [his] musical skills."

Akdong Musician last released its second studio album, Winter, in January. The record peaked at No. 7 on the Billboard World Music chart, and includes the singles "Last Goodbye" and "Reality."