"Lost in Japan" is a song born from a dream, where Shawn Mendes found himself lost in a foreign country, inspiring a cool piano part that became the song's foundation. Lyrically, it's a passionate love song where Mendes offers to travel across the globe to be with his love interest. It blends funk, pop, and R&B with "funky strings and driving bass," reminiscent of Justin Timberlake's work, an artist Mendes was listening to heavily at the time. This song plays like a spontaneous, romantic adventure, driven by a desire to bridge any distance for love.