Japan’s leading mobile game recently pushed its registered user count to nine million, according to industry watcher and analyst Dr. Serkan Toto. The free-to-play game, which is currently estimated to generate between $54 million to $75 million a month in Japan, reached the nine million mark 21 days after it reached eight million registered users.

A chart from Social Game Info shows how Japan’s current top grossing mobile game acquired nine million users since launching on the Japanese Apple App Store on Feb. 20, 2012. The explosion in growth for the game occurred when game company GungHo launched a TV ad campaign on Oct. 15, 2012.

The chart details how the game moved from three to four million users in 19 days after the TV spot began airing. Comparatively, it took the game 94 days to go from two to three million users. Toto points out that other mobile companies including DeNA, GREE and Line are using TV ads to promote games.