You get them from Egan by completing his first quest "Please Taste This For Me.Harvest Basket: An item used when caring for and gathering from monsters. It is used to gather items from monsters you've befriended. The harvest basket is received from Rosalind after finishing her quest: "Please find me an Apple". There is a line of evolution separated by weapon's type.
Most weapons could be upgraded into a better version, but more than once. As example katana derived weapons have a better critical strike ratio. If you want some more, you'r pleased to write a request on my wall ) User:Alcool007. There is some stats I could write from notes. Combined with abilities books (skill seals), make Kyle, Aaron and Aria battle style being unique. Weapons Each weapons have specific animation.
During the second part, to get the same best results, you will have to upgrade them.