there are several ways to gather those sweet umbracites:
guaranteed mission-reward as a visitor
random drop from yokais during coop-missions (tori-gate and RE)
finish twilight missions (only one per day/difficulty)
donate items to specific clans
In this video I focus on the donation-reward. you´ll also get a lot of glory and clan-points for the picked camp. However, jolly-coop as a visitor is the way to go for effective umbracite farming.
OHKO axe-build: • Nioh - LumberChop Farmin - Fastest way to ...
track: gereat - wasser
/ geraet