Hey, in your first post you said "playing in Adventurer’s Mode", but messages like "Aura works here" only appear in Story Mode.
So in Story Mode, you need to talk to Koyanskaya and sign the contract, after that you need to play "Cursed Items" scene from Corruption Tab. Then you can play the "Purchasing a Permit" node (this node is NOT replayable, you can only play it once and afterwards it will appear as locked). After that you can summon Zani, and then you need to go to the left end of the village, and interact with the sign there - the farm is now unlocked.