Gree made a splash last week with the launch of its first mobile social game for the U.S. market, Zombie Jombie. Now the Japanese company is launching its second U.S. game, Alien Family.

The first game was more than just bait for Gree’s mobile social gaming network. It hit the No. 1 spot for top free role-playing game, top free strategy game, and became No. 9 on the top free games chart. It is No. 37 on the top-grossing apps list and No. 12 on the top games of the Apple App Store. The rollout of new games is aimed at snaring a share of the mobile social game market, which Gree and its rivals believe will become a multibillion-dollar entertainment industry in the West. Gree is already a billion-dollar company, largely due to the success of its mobile social gaming network for feature phones in Japan.

The new iOS-exclusive game takes place after a catastrophe scatters a race of friendly aliens. Players help the aliens create a paradise on Earth while searching for new friends and lost relatives. The free-to-play game has more than 80 unique aliens and social features. Players create their own alien village by building, farming, fusing, and exploring. It’s the sort of cute RPG that does well with audiences in Japan. The test is whether Americans will like it.

Gree is in the midst of a big rollout of its social mobile game platform, which will debut in the second quarter. The company plans to spend $50 million to market the platform. That’s as much money as Sony is spending to market the PlayStation Vita portable gaming device.

Gree is in a race to create a platform for social mobile before rival Japanese firm DeNA grabs its own beachhead in the lucrative U.S. market, where the mobile gaming craze is just catching on and is starting to follow the pattern of Japanese gamers.

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