[5] "Lost in Japan" is a funk, pop and R&B song,[6][7] with "funky strings and driving bass" that bears resemblances to the work of Justin Timberlake.

"[9][10] Lars Brandle of Billboard wrote that the song "opens with a subtle spell of piano then changes gears with a fat bass sound and groove".

[14] Mike Nied of Idolator regarded the "atmospheric" song as "another solid gold bop", complimenting its ability "to present a new, more mature version of the superstar".

[16] Jordan Sargent of Spin praised the track, deeming it "notably well-made pop music" and "refreshingly spacious", despite being ambivalent towards his previous single "In My Blood".

The music video reenacts scenes from the 2003 film Lost in Translation, where Mendes plays the role of Bob (originally portrayed by Bill Murray).