If you're into delinquents, romance and UFO's, you should definitely check out this game.
That's the plot, but, you can also do whatever you want, such as build a relationship with one of the three girls.
Kenka Bancho: Badass Rumble has a lot to offer. It has an interesting loading screen which, instead of boring you to death, tells you interesting information about Japan and the "way of the bancho". This segment is called "Bancho 101". It's a lighthearted game, where you can either decide to take it easy or beat up delinquents. Careful, though. If you take it TOO easy, your "manliness rating" will go down.
You can buy new clothes, a new hairstyle, and even win a banana suit and a mock gundam suit at some point.
Unfortunately, that's really all it is. When it comes to combat, the game doesn't have much to offer. Aside from the special attacks called "local specialties", the combat is dull and repetitive. You can change your moves in the menu, but it will get old at some point. The storyline is not that engaging either. You'll need to look up guides if you want to follow a particular storyline, because nothing indicates where you should go, aside from annoying text messages sent every half hour.
But on the bright side, Kenka Bancho definitely has replay value. You can transfer your levels and all of your items and achievements to a New Game+. Unfortunately, you're going to have to re-defeat all of the banchos that you fought in your previous playthrough.
All in all, I do recommend that you buy this game. Don't expect a deep story or touching moments. This is a game made for humour, not for substance.