While certainly not unpopular in the Western market,
Undertale is very popular among Korean and Japanese gamers. The Korean translation of the demo, the only current official translation in a language other than English or Japanese, was made in response to fan request, with a fan translation of the full game in Korean coming out soon after its release. The fanbase in Japan is also quite large and probably more unified there, with some big names among the fans including
Yoko Taro,
Swery65, and
Hato Moa. It also received detailed entries in
Pixiv dictionary. This culminated in a much-requested Japanese localization announced in E3 2017. It is one of the few games of Western origin along with
Crypt of the NecroDancer to have a crossover/collaboration event in
Groove Coaster, a game made by
a Japanese company. As a measure of
Undertale's breakthrough popularity in Japan, it is worth mentioning that the game for a time actually managed to outsell the juggernaut
Dragon Quest XI on the Japanese PSN. This would reach a higher peak when Sans was included in Nintendo’s Smash Bros as an alternative skin.