You can equip most weapons on most characters (male characters can't use whips, iirc), but they're not all similarly proficient with each weapon. They have 1-3 star ratings to determine how well they can use each weapon type, so someone like Sun Quan can't use clubs effectively, but he's a 'master' with swords. That sort of thing. Once you find/buy a weapon, you can equip it on each character.
The moves are pretty much the same no matter which character uses them, but each has a preferred type and they get EX moves when those are equipped. Everyone gets two unique musou attacks, too, so there are things there to keep them pretty unique and different from one another.
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Knowledge is the eye of desire and can become the pilot of the soul.