In early 2009, Younha made her comeback to the Japanese music industry, now signed with Sistus Records, with a Japanese version of "Memory", titled "Kioku", tying in as the ending theme to the Rideback anime. No physical release of the song was issued, and was an online only single until the release of her next studio album, Hitotsu Sora no Shita, which included it on the track listing. 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). She went on to release 2 physical singles, "Girl" and "Sukinanda", however both failed to chart in the top 100.
Her highly anticipated third album Part A: Peace Love & Ice Cream was released on April 16, 2009, with a new record label, Lion Media. The promotional track 1, 2, 3 was a signalled change in her style, in fashion sense, taking on a cuter, girly appearance, as opposed to her more tomboy look for her previous promotional periods. 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. Despite the sudden change in musical style, the song was a strong contender for #1, but was beaten out due to strong competition during the promotional run.
On December 11, 2009, Younha released the second part of her third Korean album, Part B: Growing Season, showing a mature, darker contrast to the happier, pop-based Part A. The album spawned one #1 single, "We Broke Up Today".