Like One Distant Day (먼 후일), Unable to Forget (못 잊어) is about not being able to let go of someone from one's past. It is written from the perspective of someone who observes this lovelorn person (an arrangement we see in Rapids (개여울) as well), telling them to resign themselves and accept it as their destiny, as there is nothing that can be done about it. We do not know for sure if Kim So-wol wrote it thinking of his high school muse who had died very young, but it wouldn't be surprising if he did. For the poet, it appears such a deep rapport between human hearts was by far the most precious thing in life, seeing how it permeates his works.
A tender soul given to poetry from a young age, Kim had a tough life. He was married through an arrangement made by those around him well before he first opened his eye to love, his study in Japan was cut short in the wake of the Great Kanto Earthquake, the family mining business he had been involved with had to be closed, and the newspaper branch office he tried his hands on didn't work out either. It appears either he was very unlucky or he lacked the gift of making things work to his favor, which he really needed to navigate his way in the harsh place Korea was at the time. Kim died at thirty-two in unclear circumstances of failing health and destitution. He might have been a possessor of a soul too delicate to be very good at anything other than writing poems of heartbreak, forever yearning for his muse, as this work shows.