Endgame progression
Farm Kappa Teardrops for Eternal Rift memorandums
Yokai Teardrops from a repeatable Kappa encounter can be traded for memorandums and other stock at the Eternal Rift Sudama.
Forest of Soul Shrine in Tokaido: travel south past the initial enemies to the Kappa in the central pond. Spend Teardrops at the Eternal Rift Sudama.
Repeat the southbound Shrine-to-pond route, resting at the Shrine after each defeat. This is a repeatable farm; drops and shop inventory should be checked in-game.
Stop once you have enough Teardrops for the purchase you want, or switch to another source if the shop does not currently offer a useful item.
Open a guide to find other locations and see what the item is used for.
Yokai Teardrops from a repeatable Kappa encounter can be traded for memorandums and other stock at the Eternal Rift Sudama.