아른거려 describes the way an image, memory, or light flickers and shimmers before your eyes, not fully clear but impossible to ignore. It's a vivid, sensory word that feels much more poetic than a simple 'remember' or 'think of'.
In this song, DAY6 uses it to express how the person's smile "계속 눈앞에 아른거려" (keeps flickering hazily before my eyes). This perfectly captures the feeling of being haunted by a lingering, irresistible image of someone you are falling for, even when you know it might be foolish.
DAY6 turn adolescent uncertainty into an electrifying pop-rock confession in “What Can I Do.” The narrator is hopelessly caught off guard by someone whose mood changes every time they meet, leaving him spinning with questions: Why do you pull me close then walk away? Why do I chase you even when I know it hurts? Every fleeting smile she shows becomes a new reason to stay, even while he scolds himself for falling deeper. The repeated cry “What can I do?” captures that dizzy mix of excitement and frustration that comes with a first intense crush.
Underneath the crunchy guitars and sing-along chorus, the lyrics sketch a tug-of-war between head and heart. He lists everything he should do—stop overthinking, stop following her around—yet each time he tries, her image pops back in his mind. In the end, his simple wish is disarmingly honest: I just like being with you, even if I have no answers. It is a relatable snapshot of anyone who has ever felt powerless in the face of unpredictable love, wrapped in DAY6’s signature energy.