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Brazilian and Japanese styles differ like night and day.
If you want something to back up your kickboxing i.e. grappling and are inspired by MMA then Id say go find a BJJ school, failing that Judo or wrestling.

Aiuchi is a very good style which is based aroud 'set pieces' as in most japanese style JJ. i.e. a certain situation will be given e.g. guy tries to bottle you in this fashion and gives you a set defences to use. Japanese JJ tends to cover much more ground i.e. weapon defence, punching+kicking (though Aiuchi are one of the styles which has very little striking) throwing, multiple attackers all from set differing attacks e.g. kicks punches and weapons and does some groundwork as well.

BJJ teaches grappling on the floor i.e. groundwork. It teaches this almost exclusively and does so impressively well. Due to the level of skill in this one area BJJ guys can go and compete in a variety of competitions with differing rules and backgrounds which have an emphasis on ground grappling.

A second difference is how they train, japanese jj trains mainly with an uki/tori relationship i.e. one person does the technique the other 'allows' the technique to be performed to some degree (varies depending on the training involved).
BJJ tends to use partnered drills and progressive resistance, basically get to a point as fast as possible where you are using the techniques on a fully resisting opponent trying to do something to you back.