The following details come from official River City: Tokyo Rumble press release:

River City: Tokyo Rumble follows the story of a hot-blooded high school student named Kunio and his good friends. When a nefarious gang moves into Tokyo to try to take it over, it’s up to this self-proclaimed “fighter for justice” and his buddies to make sure the streets stay safe!

Punch, kick, use weapons such as soccer balls, iron knuckles, chains, and even bicycles to knock some sense into those devious gang members. Take on jobs, level up your abilities, and don’t forget to stop on occasion for a snack or two at the local food joints. Luckily, smiles are free!