Japan is a country that is off the coast of eastern Asia, which consists of a chain of islands. In mainstream Smurfs cartoon show, the Smurfs have visited Japan during their quest to restore the Long Life Stone and during their time-traveling adventures.
In "Smurfquest", the Smurfs travel to Japan to find the purest element of wind, which resides in the temple of the West Wind which rests high in the clouds.
In the Season 9 episode, "Karate Clumsy" and "Papa's Big Snooze", the Smurfs had been to Japan and met Mouse Master and several characters such as the emperor, Ninja Rat, and more during their adventure in Japan.