The song "Solo" by JUNNY & lullaboy talks about the regret of a breakup and how it feels to achieve success without the person they loved. The lyrics express the desire to run away and escape the pain, but at the same time, there's an acknowledgment of their own responsibility for the breakup. They ask the question of whether the relationship could have been saved if things were done differently. The song features a dreamy and melancholic melody that reflects the emotions of longing and loneliness. Ultimately, "Solo" is a song that captures the bittersweet feeling of moving forward without forgetting the past.