Within the song dayfly the singers talk about a life of full regret, specifically the topic of a one-night stand. Containing the stories of those who live from day to day, the song explores the regret that they (the speakers) have repeatedly spent impulsive nights with strangers. They discuss that although people look negatively at people who live with regrets, we are all the same people who make different mistakes. People have discussed this song as being DEAN’s most hauntingly beautiful and deepest songs, lyrically. In a press release for the single’s music video DEAN said “It’s about regret and repetitive cycles,”, sharing that this song Dayfly and his last single Instagram hold similar themes, DEAN continued “It’s about observing myself. I couldn’t see myself for a longtime. This album is about expressing who I am, who I was, and who I want to be. Someday I won’t be able to remember everything and someday I will eventually die. So, my motivation came from wanting to make my own record of my life and my legacy.”

The song showcases DEAN’s glossy vocals, complimented throughout by Rad Museum’s slightly more lively tone. The male singers' vocals are brought together by Sulli's sweet, honey voice. The song also includes additional vocals by Daniel Caesar, supporting DEAN’s lyrics. The track’s instrumentals are deceivingly simple, DEAN uses a lo-fi hip-hop beat, topped with electric guitar, similarly to his previous single “instagram.” DEAN adds flare through the introduction of the violin in the pre-chorus, the understated harmonious elements in the bridge, and the final touch provided by the whistling that brings the track to a close. DEAN’s glazed lyrics speak to those who feel lost or full of regret about themselves and notes how it’s an accomplishment just to make it through the day. This feeling of dread or repetitive struggle is not often highlighted in Korean music or media, yet instead of suppressing these numbing thoughts and conforming to societal expectations, DEAN embraces his inner darkness, setting himself free from his personal demons and producing art in its most unfiltered and genuine state. 

The album cover for the single is a great representation of how the artist wants to convey a song's lyrics through the album artwork. The broken mirror within the cover, I think, represents the harsh realisation of facing the reality of what the speakers question in the lyrics, the thoughts about a meaningless and repetitive life. The lyrics present the speakers questioning themselves, and feeling stuck in a cycle of hurt, while being desensitised from this pain and being full of uncertainty. I think the plastic film that is seen in the album cover is a representation of the trapped feeling in the song, as well as the broken mirror representing the hurt and broken nature of the speakers. When you finally understand it, the lyrics suddenly turn so depressing yet so beautiful, and poetic. Which I think is the same for the album cover.