The app, which is named after the Mii characters in the Wii console, was expected to be a flop, but is now the number one free download in Japan’s app store, according to App Annie. Miitomo’s popularity could be a lifesaver for Nintendo, which has long been criticized for coming late to the app business and has fared especially poor since last summer, when the Wii U console didn’t sell as well as expected. Nintendo’s first announcement that it was making Miitomo in October was also met with frustration, as it didn’t feature beloved Nintendo characters like Mario and Zelda.

Miitomo allows users to create cartoon avatars and a profile based on interests like favorite books and movies. Users can then interact with other Mii users and friends and share in-app selfies on Instagram, Twitter, and Facebook. Clothes and other items for the avatars can be purchased using virtual currency, which can be bought with real money.

Nintendo says the app will launch in the US and other countries around the world by the end of the month. Miitomo’s success bodes well for the five other games Nintendo has promised to release by March 2017, which are likely to include company mascots like Mario and Donkey Kong.