The end of the 18th episode used lines directly from a poem in his collection of works titled 'You are the only sentence I could not throw away'. The lines were read by the male lead as a narration at the wedding scene.
The poet wrote, "My words were stolen. The lines used as narration at the ending of the 18th episode during the SBS drama 'Should We Kiss First' is a poem that was included in my collection 'You are the only sentence I could not throw away'. Before my readers informed me, I've never been contacted about it and I never gave permission. They used it without my permission. Not even as a quote, but as narration. I guess they thought it was okay to use it as a short monologue since it was two sentences."
The drama revealed the writer had written that the source of the lines were from the poet. However, the credits were left out during the production. They said, "We apologized to the poet. We are making sure that viewers will see the source during the rerun and online."