yeah well i'm like at lvl 51 and apparently when you get to the final boss or before you fight him you should save the game then level up some more then fight him
cause my friend beat the game already and when you defeat the final boss you can't save it you just see the ending then that's it, that's all i know so far i'm going to finish it later
and Good Luck with Beating Riku, he also took me a couple times before a found a way to beat him