Childhood friends Lina, Mooni, and Jooyeon share a bond that's lasted through every season of their lives - until Jooyeon's journey as the sixth member of the rising K-rock band Xdinary Heroes pulls them into a world of music, dreams, and unexpected challenges. As Lina and Mooni step into this vibrant new chapter, they find themselves navigating the dazzling spotlight, complicated friendships, and the bittersweet tension between chasing dreams and holding on to the past. With the six boys of Xdinary Heroes carving their path through fame and music, lives intertwine in ways none of them could have predicted - and every heartbeat feels like a note in a song still being written.