Mugi

I'm still relatively new to VN's, with only 5 under my belt so far. I was about to start Little Busters, but then saw that a patch for something called Little Busters! EX was getting made and was close to being finished. Is this a completely different game and will I have to buy a copy of it along with the one I already have? Or is it just a patch for the base game? It looked to be like the restoration patch for If My Heart Had Wings, but adding more content, but I wasn't sure.