Kim Sejeong is making her long-awaited comeback to the music scene.

On December 8, she unveiled the comeback poster and moving poster for her new single Solar System, marking her first musical release in approximately 2 years and 3 months.

She returns with a winter-themed track following her first full album Moon, released in September 2023. The newly revealed posters highlight a classic, atmospheric mood that hints at the song's emotional direction.

Kim Sejeong began her solo career in earnest with Flower Way in 2016, achieving No.1 across major streaming platforms. Since then, she has expanded her musical identity by taking part in writing and composing tracks for releases such as her mini album Plant, digital single Whale, and mini album I Am.

Her full-length album featured lyrics written entirely by her, further solidifying her unique storytelling voice. She has also built a strong presence through numerous drama OSTs, including "If Only" (The Legend of the Blue Sea), "Meeting Again" and "Back to You" (The Uncanny Counter 1 & 2), "All My Days" (Crash Landing on You), and "Two People" (Drunken Romance).

Currently, Kim Sejeong stars as Park Dal in the MBC series Where the Moon Flows Over the River and is preparing for her 10th-anniversary fan concert tour. Beginning in Seoul next January, she will meet fans across eight global cities through the 2026 Kim Sejeong Fan Concert: The 10th Letter tour.

Her new single Solar System will be released on December 17 at 6 p.m. across major music platforms.