Formed in 2002, the duo has released eight albums to date: two self-titled records in 2002 and 2003, Library of Soul in 2005, Black Sun in 2007, Baekajeolhyeon (백아절현) in 2009, Hexagonal in late 2009, Asura Balbalta in 2011 and Unplugged in 2012.

[3] Gary, Gil, and Diggity collaborated to form a "Leessam Trio" (sam means three in Korean), and released a compilation album called 2000 Korea in the year 2000.

[5] With no formal musical training, the duo learned as they were producing by spending 400 hours straight inside the studio.

Many credited the perfect blend of Jung-in, Gil and Gary's voices as one of the reasons for the song's success.

Jung-in once again provided the female vocals for their second hit song "Leessang Blues", written and composed by Gary.

Gary said in episode 98 of Strong Heart that they were so "unknown" that they were blocked by security when they came to receive their first major award.

The title track, "Champion", was dedicated to boxer Yo-Sam Choi, who was very close to Gary and Gil.

Leessang and Ryoo Seung-Bum toured to Sydney, Australia for the first time in this year with show producer Leonard Dela Torre.

[citation needed] Gary revealed on Strong Heart (TV series) that the inspiration to his songs "Leessang Blues", "I'm Not Laughing", "Ballerino", "Girl Who Can't Break up, Boy Who Can't Leave" and "You're the Answer to a Guy Like Me" was his ex-girlfriend of almost 7 years.

It was a fulfillment of their long time dream to collaborate with different artists from different genres, using a full band via an analogue recording.

[17] In December 2012, they performed a one-night only show with the band YB with whom they collaborated for the song "Someday", "Run" and "Madman".

[18] On July 14, 2015, Leessang reached the top of multiple charts with their single "Kaleidoscope" featuring Mi Woo.

[20] Leessang has been respected even before their mainstream success despite signing with a fairly non-mainstream label, rather than a well-known large K-pop entertainment company.

Leessang are known to write and produce their own songs, direct their music videos, and keeping their private lives separate from their professional work.

However, since the success of Hexagonal, Asura Balbalta and Unplugged, they have been known to support themselves despite not receiving media attention based on their attractive looks.