Miitomo, Nintendo's first smartphone app, reached the milestone of 4 million users in the middle of April, sustaining its popularity after topping 1 million users over the app's first three days since it was released in Japan.

In addition to the 4 million monthly active users, Miitomo was reported to have 1 million daily active users, proving that the app is not a one-hit wonder.

The smartphone app has now completed an even more impressive feat, as it now has more than 10 million users after just over two weeks from reaching the 4 million mark.

Described as a free-to-start social experience, Miitomo was said to have already initiated over 300 million conversations, with over 20 million Miifotos, or pictures where Mii characters are inserted, created by users.

According to Nintendo, in celebration of reaching the milestone of 10 million users, it will be running a 10-day "Celebrating 10 Million Users!" promotion, which will run from April 29 to May 8. No information has been released regarding this promotion so far, though there is a possibility that it will allow users to acquire exclusive, limited edition items for their Mii avatars.

Miitomo is a free-to-download mobile game, but it is also considered as a social network. In the statement announcing the app reaching 10 million users, Nintendo also revealed its future plans for mobile games that will follow a more traditional route.

According to Nintendo, the next two mobile apps that it will be releasing will be based on the popular Animal Crossing and Fire Emblem franchises, with the games to be released in the fall season. The Animal Crossing app will serve as a companion app for the game on Nintendo consoles, while the Fire Emblem app will be a standalone role-playing strategy game.

While waiting for these apps to land, Miitomo users will likely continue creating Miifotos and initiating conversations. With the popularity of the app still going strong, it might not be long until its monthly active users figure doubles to 20 million.