After pivoting about five times in 2011, PocketMath co-founder Casey Grooms stumbled upon the concept of real-time bidding by chance at a party. Singapore-based self-serve mobile advertising platform PocketMath announced earlier this week the raising of a US$10 million series A funding round from Rakuten Ventures – what it claims to be one of the largest series A rounds in the island-state. The investment is part of the latter’s $100 million startup fund – launched earlier this year – focusing on firms in the U.S., Israel, and greater APAC.

It is rather unusual for any VC firm to close a series A round by themselves. The fact that PocketMath processes over 20 billion mobile ad impressions per day, as it claims, might have had something to do with that.

“We funded the entire round because the team is amazing, and the tech they’ve built out hit the sweet spot in the industry like no other company in range of opportunity,” says Rakuten Ventures managing partner Saemin Ahn, who will be joining the startup’s board. He knows this scene well, admitting that he is “kind of an ad tech geek.”

According to Ahn, PocketMath will play a critical role in growing the Rakuten Marketing ecosystem in the near future. “This investment gives Rakuten a strong stake in the mobile advertising game,” he adds.

Apart from establishing a deep strategic partnership with Rakuten, the funds will also go towards hiring talent and accelerating product development, according to an official statement.

What’s even more interesting is that this is the startup’s first round of outside funding. Since being founded four years ago, the team has managed to work its way to an eight-digit revenue, and have along the way grown a team of 40 scattered across five cities – Singapore, San Francisco, Mumbai, Sydney, and Washington DC – though most of them remain in Singapore. According to Vasudha Srinivasan, marketing manager at PocketMath, they are now looking to expand into Shanghai, New York, and Tokyo as well.