Fights upgrading weapons?

[Ygdrad]

So some fights seem to be upgrading weapons and I'm not sure why or how this works. Anyone have an idea?

[Phishfood]

I think what is actually happening is that enemies are dropping pictos or weapons on defeat, if those drops happen to be a higher level than what you already have then it replaces it with the higher level one.

I found a trader that was selling weapons and some of those weapons were higher levelled versions than what I got, so when I bought them it just replaced my old one. I don't end up with 2 of the same weapon.

[marsHm311oW]

In the open world kill every enemy at least one time. They might drop weapons and pictos, but only one time. Farming up until lv 20 isnt possible.