[4] As a teenager, Younha said she went to as many as 20 auditions with South Korean record labels but was rejected because she wasn't "pretty enough to become a star.

[6] After arriving in Japan in January 2004, Younha released her debut single, "Yubikiri," that September, followed by the Japanese version of the song in October.

[9] However, Younha's next three singles, "My Lover", "Te wo Tsunaide" and "Ima ga Daisuki", despite various tie-ins such as Bleach GC: Tasogare Ni Mamieru Shinigami, Jyu Oh Sei (獣王星) and Jang Geum's Dream, failed to replicate the success from her earlier efforts, all ranking in the lower half of the Oricon Top 100.

In the meantime, Younha enrolled in Hankuk University of Foreign Studies[6] and began her debut in Korea, releasing a digital Korean single album titled "Audition".

Exactly two months after "Hakanaku Tsuyoku", Younha returned to Korea to release her first Korean album entitled The Perfect Day to Say I Love You (고백하기 좋은 날, Gobaekhagi Jo-eun Nal).

On July 14, 2007, Younha appeared on the Korean GomTV MSL Grand Finals (a StarCraft tournament) and performed in the opening ceremony.

Riding the success experienced in Korea, her very first Korean single "Audition" was re-released on March 14 as a physical CD, limited to 10,000 copies.

Epic Records quietly released a "best of" Japanese album/music video DVD of Younha's work to date, SONGS -Teen's Collection-, on March 26, 2008, signaling the end of her contract with the record label, due to the recent poor performance of her singles, and her focus on the Korean music industry.On August 28, 2008, Younha followed up her last few successful albums with her sophomore effort, titled Someday.

Her return to the industry also included a role in a Japanese movie, On Next Sunday (今度の日曜日に, Kondo no Nichiyoubi ni), released in April 2009, also singing the theme song On the Other Side of the Rainbow (虹の向こう側, Niji no Mukougawa).

Her highly anticipated third album Part A: Peace Love & Ice Cream was released on April 16, 2009, with a new record label, Lion Media.

[6] The style change also encompassed her music, with her songs from the album losing her trademark debut Piano rock sound which brought her critical acclaim and success, turning to pop.

[14] The album features Younha's work with i-dep and Sotte Bosse's Nakamura Hiroshi, as well as popular acoustic guitar duo Depapepe.

[15] On July 12, 2011, it was revealed that Younha was suing her company, Lion Media, to request a termination of contract due to questionable validity,[16] through the legal courts, though further revelations showed that these proceedings had started since April.

[18] It was not until February 2012, that the courts found the case in favor of Younha, resulting in the annulment of her contract with Lion Media, as well as 100 million KRW compensation.

She achieved her first #1 single in her career on the Gaon Charts, 10 years after debut, with her solo remake of her 2008 hit with Epik High, "Umbrella".

On November 11, 2015, Younha released her single "Thinking About You" (널 생각해), produced by Lee Chanhyuk of Akdong Musician.

The latter contained the song "Winter Flower", a collaboration with RM from BTS, which Billboard called "an epic, comforting power ballad".

[32] "Event Horizon", the lead single from End Theory: Final Edition began to rise in the charts and viral popularity 6 months after initial release, as Younha did major gigs at universities and festivals in the second half of 2022, with positive word of mouth and fan footage gathering views online.