How do you get sword on harvest moon?

Answer 1

To get the sword, you have to reach the bottom of the second mine. On the last floor, you have to destroy all of the monsters to make the big rock blocking your way disappear. In that room will be the Legendary Sword.

Answer 2

You can use this sword to clear away the large rocks that protect the Super crop field behind the waterfall. To use the sword to destroy the rocks, place it in the red slot in your rucksack then press the A button. You will swing the sword and the giant rocks will go away. The sword's main use is just for destroying the large rocks. You can also use it to fight off the creatures in the mines if you equip it and press the Y button. If not, you can just store it inside your house once you're finished with it.