basicaly it works like this,if you bring to level 40 a character that permanently leaves your party,they drop a special item,one of these special item is a sword that's stronger than end-game weapon and you get this halfway trough the game.....
star ocean 2 has a similiar exploit,at a certain point in the game you can pay 10.000 to buy a pickpocket gauntlet which let you gain items from NPC,10.000 is an exorbitant price for that point of the game,BUT WAIT! there is an enemy that drops an item which you can sell for 1000 bucks,so you can actualy get the gauntlet even at that point,after you get the gauntlet you can return to an earlier city and steal stuff,one of the NPC has an item that generate 3 random item picked from every item in the game,HELLO END GAME SWORD!
radiata stories has special training battle which yield huge amount of experience