A great game all in all, but when you finish there isn't really that much left to do and it will leave you wanting more.
D.O.N is basically exactly like Super Smash Brothers but with all the known anime characters instead. For GC the buttons are the same too, the only difference is that you don't jump with 'X' but with 'A'. The 'Y' button is for special attacks, here are all the well known moves like Goku's Kamehame-Ha, Luffy's Gum Gum Pistol and Naruto's Shadow Clone technique. Like I said earlier you jump with the 'A' button, the 'B' button is for totally normal punches and kicks and basically the one you start doing a combo with. The 'X' button is the badass one, this is the Ultimate Move button, here you have all sort of crazy extremely strong attacks like Sasuke's Chidori, Vegeta's Final Flash and Chopper's Arm Point Transformation attack.
I think they did great with the DBZ characters making it only possible for them to level up to Super Saiyan 1 and not beyond which would be total unfair for the other characters from Naruto and One Piece. With the fact that DBZ characters can fly they also did a great job on that which allowing a character to fly in mid-air with tapping the control stick in the direction you want to go and they fly away but this costs from your Special meter so use it wisely. The stages are pretty good too, although there was 2 really annoying stages for me, the heaven beanstalk thing from One Piece where they fough God Enel and The Forest Of Death from Naruto, these stages are fast pased and just plain annoying, you have to think about how to survive AND fight your opponents at the same time.
Now to the "Story Mode". Here you basically just have to beat a few guys and get to Cell or Buu at the end and kick their asses and you're done. But you WILL get missions along the way, this is real annoying cause it stands in japanese and each time you're like "What the hell am I supposed to do?!?!?" but with a mission translator you should be fine. Why you need to carry out missions id cause then you get money, and money are used at the slot machine after you beat Cell or Buu. This slot is ANNOYING, believe me this slot is rigged, you never win and you ge tpissed each time, but still you have to play it cause this is where you get characters, stages etc.
But all-in-all this is an awesome game, my only complains are, it should be more characters, a few more stages and get rid of that damned slot machine. But other than that it really is awesome, but if you're not a fan of any of the shows you might not enjoy it as much as I did.