Weapon Duplication Trick
Select “Item” and press A on an empty slot during a battle. Move up until the equipment in that character’s left and right hands appears. Press A on the weapon to be duplicated. Press B and complete the battle or retreat. After the battle, equip that character with their weapon in the same hand it was in. The weapon should have a “2” next to it. Unequip, then re-equip the weapon. You should now have one copy of the weapon equipped and another one in your inventory.