C443 New Alchemy Methods and Anti-aircraft Guns

It was rare for Lorenzo to be home today.

But this was not because he was resting today, but because his teacher had urgently summoned him - his best friend Leonardo had invented a new thing.

After lunch, they sat face to face in the living room. In front of them was a gold ingot, a scroll of drawings, and a few documents.

"This is the gold I refined. You can take a look at its color