Anyone know where is their location? Got all Buddha stones (from all castles) and it's time to go to the Mountains.

Nothing comes up in Google or guides.

Put all four Buddha items on one piece of equipment and they will have additional boost, giving that piece 90% resistance to all elements, Since elemental resistiance caps at 75%, you can then focus on ki increasing jewelry and masks with high damage reflection and ignore their resistance boosting properties. Death maidens and tengu seem to have a high drop rate of kenja stones (all varieties), where mid to high level tengu also have a high drop rate of unique weapons and armor pieces. Just save, kill and reload until you get the items you want.