Sung Si-kyung (Sung Si-kyung's Instagram)

When temperatures drop and leaves begin to change color, many Koreans turn to Korean ballads, wallowing in the lonesome mood associated with falling leaves and the passing of the year close at hand. Numerous artists have continued the legacy of these nostalgia-evoking Korean ballads known for their soft vocals and sorrowful melodies.

Sung Si-kyung -- 'On The Street'

When talking about Korean ballads, singer Sung Si-kyung is almost always mentioned. His uniquely beautiful and expressive voice has gained him immense popularity.

Sung debuted in 2000 and has numerous hit songs including “On The Street,” one of his signature tracks.

Released in October 2006 as the main track of his fifth studio album "The Ballads," the song was composed and written by Yoon Jong-shin, a singer-songwriter who now leads the K-pop agency Mystic Story.

Yoon initially created the song around 2002 or 2003, and had offered it to several female singers who refused it because of its difficulty. Sung discovered the song while visiting Yoon's studio and the rest is history.

Kyuhyun (Kyuhyun's Instagram)

Kyuhyun -- 'Slow, Slowly'

Kyuhyun, the main vocalist of the boy group Super Junior, first revealed that he can sing ballads with the release of his first EP "At Gwanghwamun" in 2014.

In "Restart," the first album with his new agency Antenna released January, the third track “Slow, Slowly,” stands out from the rest -- it is closer to the ballad style Kyuhyun has become known for. The song's lyrics reflect the narrator's slow but eventual acceptance of a breakup, something many listeners can relate to.

Na Yoon-kwon (Na Yoon-kwon's Instagram)

Na Yoon-kwon – 'If It Was Me'

Singer Na Yoon-kwon first made a name for himself when four of his songs were included in the soundtrack of "First Love of a Royal Prince." Although the the 2004 MBC drama was a flop, "If It Was Me" from the soundtrack gained attention, leading to Na's official debut in September 2004 with his first studio album "Addiction."

With heartfelt lyrics expressing the unrequited love of the narrator delivered in Na’s soft voice, “If It Was Me” remains a beloved song and still ranks high on karaoke charts in Korea.

Na debuted at a time when popular artists like Kim Jong-kook, Lee Soo-young and rock band Buzz were at their peak. Rising stars like Lee Seung-gi, TVXQ and SG Wannabe around the same time also overshadowed Na.

However, Na has continued as a ballad singer and, as of the 20th anniversary of his debut, is still releasing new songs.

The singer held his 20th-anniversary concert "Recording" over the weekend and released the single "If I Were" in September in celebration of the milestone.