Everyone in South Korea is on KakaoTalk. Out of the smartphone penetration rate of 73%, 93% use the mobile messaging app Kakao, according to Nielsen.

So it's no surprise that they are expecting to generate about $200 million in revenue this year. Last year they made $42 million, with a profit of $6.5 million.

The messaging app is looking to grow, but it may be harder than it seems. Line is already really popular in Japan. WeChat dominates China. Whatsapp is elsewhere.

To grow out of their own market, Co-CEO Sirgoo Lee aims to take a piece of Indonesia, the Philippines and Vietnam before rivals can spread there. And to do that, it'll have a lot of customization.

Kakao already adapts its software to each market by recruiting local artists to make virtual stickers sold through the app. Lee is looking to mull localization even further.

Will they be able to do it? Have you tried Kakao talk yet? Or do you have your own favorite?