Director Guillaume Senez was inspired to write the film after learning about post-divorce parental custody rights in Japan.

[1][2] To aid in their research, Senez and actor Romain Duris met with three French nationals who had lost custody of their children due to Japanese law.

"[9] Aurore Engelen of Cineuropa wrote, "Buoyed by a super-efficient screenplay, composed of little nothings which result in this impossible encounter, taking a chiaro-scuro path towards a resolution that's as luminous as it is doomed from the outset, A Missing Part explores both a father’s obsession and the irreconcilable otherness of a foreigner or stranger.

"[10] Paul Enicola of The Asian Cut complimented Senez's direction in portraying a "deglamorized Tokyo...allowing the city to emerge as a character in its own right.

And with the urban landscape mirroring Jay's estrangement and alienation, the film [emphasizes] his growing sense of disconnect from a world that has always felt foreign to him.