[7][A] Hien Nguyen of The Kraze describe the song as having mysterious and dark vibes that talk about falling into someone deep and are reminiscent of their previous title track "Oh My God.
[8] Writing for Genius, Sofia Gomez wrote the song "reaches the point of losing yourself with an erratic emotional shift" that will give a "mysterious aura" to the listeners feeling goosebumps.
"[9] In his album review for The Korea Herald, Park Jun-hee remarked that "X-file refers to a case deemed unsolvable".
He pointed out that in the song, (G)I-dle 'continuously declares, "Kill the truth/me, and you/I cannot end anything" – [whispering] a dark truth into people's ears, its [sic] no doubt that this track will be added to many playlists.
'[10] Madison Murray writing for The Honey Pop cited it as a " normal love song" in the EP but with "a bit of twist".
There is a scene where Miyeon and Yuqi wander with empty eyes behind the gorgeous visuals, and the dark atmosphere is doubled throughout the video.