From the introduction:
Welcome to Zawame City, Jumper! This is an island city resting just off of the shore from Japan, though not very far off. This used to be an ordinary suburb until the Yggdrasil Corporation bought it and used it for development, changing it into a sprawling metropolis with jobs and business aplenty...albeit under the thumb of said Corporation. Among the everyday youth are the Beat Riders, dance gangs who regularly compete for stage dominance in a way of escaping the almost totalitarian grip Yggdrasil has on their everyday lives, or just to get away from day to day life pressures in general. Recently, a new popular pastime called the Invess Game is gaining popularity, involving summoning strange, tiny monsters using Lockseeds... and they seem a little more dangerous than your average hobby trend...