Announced last year, Nsquare is the joint development studio formed by Nexon and NCsoft. In the CG trailer for MapleStory 2 revealed today, it was confirmed that Nsquare is the team behind development, being the 2nd game after Mabinogi 2: Arena. Nsquare is also currently hiring for a 3rd game.
Over the past months, Nexon has also revealed several 3D models for the characters and monsters found in MapleStory 2 (more here). MapleStory 2 will be a full 3D MMORPG, vastly different from its prequel. Both games will be operated alongside each other.