The Legend of Zelda: Link's Awakening/Key Cavern

Since you completed Bottle Grotto, you don't need BowWow to continue the quest. If you keep him around, he can still help you in combat, or help detect the locations of Secret Seashells, but neither Richard nor the monkey will help you.

Exit to the right, and find Richard's Villa. He gives a quest to find the Golden Leaf in the castle. There's five leaves to find, and you'll need to get a shovel. Purchase it from the store if you haven't already.

You will also need to start on the Trading Sidequest. get the Yoshi Doll from the store and trade it to the northern house for a ribbon. The ribbon is given to the chain-chomp puppy for Dog food. The dog food is then used to purchase bananas.

With the bananas, you can head to the castle. The moneys will build a bridge for you, to the right of the castle. In addition, you will receive a stick for the trading sidequest.

Golden Leaves

Continue north, and turn west. Slash the bush, and continue underground into the castle. There are five leaves to collect:

1. To the right of a castle is a set of six holes. Hit the Mad Bomber as he pops out, and dodge the bombes he throws. He drops a leaf when defeated.
2. To the left of the castle is a bird sitting in a tree. Startle the crow with a bomb, and defeat it for the leaf.
3. Enter the castle. In the second room, eliminate the enemies for a leaf.
4. Head upstairs. Bomb the two wall statues in the first upstairs room to detach them from the wall. Defeat them both for the leaf. (If you don't have bombs, you can harvest some in the room before the final leaf.)
5. Exit to the south, and re-enter by the center doorway. The door will block progress, but you can grab an urn and throw it to smash it open. Continue north and defeat the Ball & Chain Trooper.

Return to Richard, and he will open a passage for you. The passage leads to the pothole maze, which you gradually reveal by cutting away the shrubs. There are diagonal shortcuts available if you want to speed through it. At the end of the maze is an owl status overlooking some grass. Cut the grass, and dig in the empty spot to get the key for the third dungeon.