The Nioh 3 Dirty Key is an item that opens a door in the Tenryu River area. Inside the locked house, you will find a chest that contains the Armor Piercer secret skill text.
Let’s see what you must do to get this Nioh 3 key and collect the skill text!
How to Obtain and Use the Nioh 3 Dirty Key
To get the Dirty Key, you must defeat the Yamainu enemy that patrols the village. The Yamainu can be a tough enemy, especially if your level is below 6.
How to Find and Defeat the Yamainu in Nioh 3
The Yamainu can be found wandering in the village. This is not the only enemy you will encounter here. To make the fight a bit easier, you should first clear the area.

Starting from the village entrance, jump on the roof of the houses on the right. Take care of the enemy on the roof and wait until you see the Yamainu patrolling the street. This is a good moment to catch the enemy by surprise. Sneak and knock down the Yamainu, then finish him off with your attacks. Don’t forget that you can also deflect his attacks.

Defeat the enemy and collect the Nioh 3 Dirty Key. You can now unlock the door and obtain the Armor Piercer skill text.
Where to Find the Locked Door and Use the Nioh 3 Dirty Key
After defeating the Yamainu and obtaining the Dirty Key, continue uphill to arrive at a house with a firepit outside.

Use the key to unlock the door and enter the house. On the right, you will find a chest containing the Armor Piercer secret skill text and a couple of other rewards. The Armor Piercer increases the damage of the final blow and grapple by 10%.
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