The story in the CN version goes very far but I doubt we will get it all on release, hopefully we will get constant updates with new level caps/story as people reach the caps.

The story follows naruto as far as I remember but some things do change to make it a more interesting game. I don't want to spoil it if your a story buff so you'll just have to play and see. But you don't always have your team in the story battles.

You interact with the characters to get quests, thats about it. After you get the quest you enter an instanced dungeon. You can explore and fight enemies in the overworld but yur main does not get exp for them, they are a free version of food.

If your not sure about the mmo aspect then just ignore the other people and play at your own pace, guilds help you be stronger and you need to play with people for some events but you can do the story by itself and just enjoy that if its your thing.