Every night, Yeo-un takes the last train home—same route, same time, same routine. But one thing keeps catching his eye: a girl with a guitar and a presence that lingers in his mind. When a shared love for the indie band Long Afternoon sparks a conversation, their late-night encounters begin to turn into something more. But Hae-in isn't just another fan—she's the voice behind the band, a secret she can't afford to reveal. As music draws them closer, the truth may threaten to pull them apart. When the final note plays, will their story end in harmony... or heartbreak?