Japan’s mobile gaming market is huge, but just a few games take home a bulk of that spending. And one is making an extraordinary amount of cash on a daily basis.

Developer Mixi, which produces the Japanese megahit Monster Strike for iOS and Android, reported that the game made $378 million from April 1 through June 30 (via gaming analyst Serkan Toto who specializes in the Japanese market). That comes out to $4.2 million for each day of last quarter. That’s actually up from the $3.8 million that Monster Strike was making every day of the previous quarter from January 1 through March 30. It seems like Mixi’s game is well on its way to racking up more than $1.5 billion over the course of 2015 and through the developer’s fiscal year, which ends March 30, 2016. That puts it right new to other mobile megahits like Puzzle & Dragons, Clash of Clans, and Candy Crush Saga in terms of revenues.

“The game isn’t showing any signs of weakness,” analyst Serkan Toto wrote in his blog. “What is especially astonishing about the Q1 figures is that close to 100 percent of sales come from Japan alone.”

Toto points out that Mixi is shutting down the game in China, where it has flopped.

In addition to the Japanese monopoly on Monster Strike spending, the game is also notable for arriving at its success while Mixi only spent $21 million on advertising through the quarter. That’s only $230,000 for each day that it was making $4.2 million. Developers were spending half of that amount just for the air time to market games like Clash of Clans during the Super Bowl. And that doesn’t include however much Clash of Clans developer Supercell had to pay actor Liam Neeson to appear in those commercials.

“On an annualized basis, global companies like Supercell generated only slightly more sales lasts year while spending 4-to-5 times more per day on advertising,” said Toto. “[So] it pays to be the leader in a high-value, largely closed market [like Japan].”