How to Get Koholint Sword
The Koholint Sword can be purchased or traded from the Seashell Mansion. In this mansion, there is a spirit that resides here and is a friendly one that has a few things to trade in return for Seashells.
The Spirit of the Mansion asks for Seashells in exchange for the various items it has in its possession. To get the Koholint Sword, the Spirit asks for 20 Seashells. Seashells are items that are usually found buried underground and can be found hidden all throughout the areas, corners, and nooks of the game.
In total, there are 50 Seashells that you can find in the game, however, you are just required to get 20 if you are looking for the Koholint Sword. Once you have all the 20 Seashells in your hand, you can then head back to the Mansion and then talk to the spirit for trading the shells for the sword. This way, you can get the Koholint Sword for yourself and use it to slash down enemies.