Just for the story? Well, there's a tiny bit of info about Rico and Flowen if you choose to play one of the quest arcs, which is very slightly more interesting, but to get the whole story, you'll have to play through the game six times, once for each main character, all offline!
Main Characters:
Heroside: HUnewearl, RAmar, FOmarl
Darkside: FOmar, RAcaseal, HUmar
(You cannot customise their appearance or special abilities, only their decks.)
You don't really need to know any history about Break and Orland. If you did Blue Star Memories (under the same hunter license), you can gain access to an extra download quest. That's all really. They don't even remember you when you talk to them offline

. So there's not-- *

peech: remembers that she's supposed to be trying to convince someone to buy the game*
Heroside is also called Hunters, and doesn't just contain HUnters. Each side has 12 characters (one of each class), so there're 24 characters in all.
The Darkside is also called Arkz.
Have you seen the 24 characters you'll be playing with? This site gives some information:
http://www.phantasystaronline.it/ep3characters.html
Too bad if you don't like the look of them. You'll be stuck with them for the entire game

.
The speed is slow compared to Ep1&2 due to the nature of the game. There are no new costumes. Give the card-battling a chance. It wasn't half as boring as I thought it would be.
The characters were cute enough.
