ILLIT, the rising K-pop group, marks Yoona and Minju’s first OST release with The Moment I First Saw You, I Thought of You All Day for the KBS 2TV drama Last Summer. The track, serving as the drama’s fourth OST, drops on November 15 at 6:00 p.m. on major streaming platforms.

The mid-tempo pop track captures the fluttering heart and earnest confession of a first love. Yoona and Minju lend bright, dreamlike tones, while a breezy whistle motif and sleek electric guitar drive the melody, heightening the drama’s immersion. The lyrics convey the lingering sweetness of first love, with lines that evoke the crush’s lingering memory.

The song’s production is led by Song Dong-woon, a producer noted for overseeing the Last Summer OST. He has previously worked on hits for dramas such as Hotel Del Luna, Descendants of the Sun, Goblin, and other acclaimed projects, including the OSTs First Snow Like You, Stay With Me, Beautiful, and I Miss You.

Last Summer premiered earlier this month on KBS 2TV, following a remodeling romance between childhood friends who confront the truth about their first love. IllIT’s Yoona and Minju perform the OST Part 4, which will be available to stream on major platforms from 6:00 p.m. on November 15.