Short Name. Big Booth. Mystery to Westerners.

This booth was one of the biggest booths at the Tokyo Game Show. It took up one tenth of the entire show floor. It wasn't Sony's. It wasn't Square Enix's. It wasn't Capcom's. The booth belonged to Gree. So what the hell is Gree?

Gree is a Japanese mobile social networking service, with over 26 million users in Japan. Since acquiring U.S.-based smartphone platform OpenFeint earlier this year, that number has jumped to over 123 million people globally.

Not bad for a company that was started by Yoshikazu Tanaka in 2004 on his personal website.

That's a staggering number of people. Gree offers cross platform apps for operating systems and phone carriers that allow Gree and, outside Japan, OpenFeint users to communicate and keep tabs on each other while gaming on their cell phones and smartphones.

While Gree has only released a handful of apps, it offers thousands of them for players to download and play. There are in-house social games like Decobito (think Animal Crossing but with dwarves) and Cerberus Crusade (a mobile RPG), but the game that started it all was 2007 fishing game Tsuri-Sta, which, according to Gree, is the world's first mobile social game.

In Tsuri-Sta, players do more than just fish. They can collect fishing equipment, collect fish prints, organize a fishing team with their friends, and even compete online. As I played the game at TGS at the Gree booth, I found it be quick, casual fun—even after all these years.

"What Gree really excels at," a Gree spokesperson later told me, "was our know-how." Since Gree is cross platform, it also brings friends on different devices to game. It's like Facebook, but with a stronger gaming bent. Gree also offers messaging and even a dictionary service to members. Gree's bread and butter are in-app microtransactions and in-app banners.

These days Japanese gaming is all about the social experience through phones. No wonder Gree is rapidly expanding, inking deals with a Chinese online community provider, which has 650 million members. Big studios, such as Sega and Konami, are releasing games for Gree. Smaller Japanese studios, like Keiji Inafune's Comcept, are, too.

The goal, according to Gree, is to have a mobile gaming platform with over 300 million members, with plans to even publish social e-books in Japan next year and release its Gree branded games in the U.S.

In year's past, Japanese mobile phone carrier Docomo had a huge TGS booth. This year, Docomo did not. And from talking to a handful of the Japanese game press, no other company seems to arouse Japanese gamer ire and fascination for much the same reason that Western gamers turn their noses up at social games.

So what's Gree? You might not know now, but you will.

(Top photo: Brian Ashcraft | Kotaku)

You can contact Brian Ashcraft, the author of this post, at bashcraft@kotaku.com. You can also find him on Twitter, Facebook, and lurking around our #tips page.