This part will take you through the start of your quest.
You start off at Outset Island after the introduction to the whole story plays. The location also serves as a tutorial for how to use the controls for our hero. Aryll, a young girl, calls out to her brother Link, who is at the top of a tower called Aryll's Lookout sleeping. She will remind Link upon awakening that today is his birthday and that their grandmother has something important to give him. Once we have control of Link, climb down the ladder and follow the path that heads to the west across the bridge until you reach the house that's far to the west. Before you go into the house, though, go near the porch and crouch down so that you can crawl underneath it into the basement where you'll find a treasure chest that contains an orange rupee worth 100 rupees -- a good way to start off! Now crawl out of the basement and enter the house, then climb up the ladder to the loft where Grandma is waiting for you. She will now give you the Hero's Clothes, which serve no purpose other than to make Link look like the legendary hero. She will go on to talk about the shield hanging on the wall while Link puts on the clothes, then she'll tell him to go get his sister while she's making preparations for his birthday party.
So head back to Aryll's Lookout, where Aryll will comment about Link's new clothes and then give him his birthday present -- her Telescope. She will direct him in the use of the Telescope, so we might as well follow her instructions. First equip it to one of the buttons used for items. Next, aim the telescope at the bird-like being who's near a mailbox. After that, aim the telescope up. You'll then see a big bird carrying a young girl in its talons, being chased by a pirate ship firing cannonballs at it. One of the cannonballs hits the bird dead-on, causing the girl to be dropped into the forest at the top of Outset Island. Aryll will then say the girl needs help, but it's too dangerous for Link to go up there.
Fortunately, Grandma told Link about an old man named Orca, who knows about swordplay. Head back towards Grandma's house, but this time go to the first house on your left, using the door at ground level to enter. Inside you can talk to Orca, who senses from Link's face that something serious has happened that requires our going to him. He will now take you through a tutorial on how to use the sword, which you'll have to pass through in order to get our first essential item, the Hero's Sword.
With the Hero's Sword on hand, head back toward Aryll's Lookout, but this time take the path that leads uphill, using the sword to slash through the small trees blocking your path. Continue up the path until you reach the bridge on your left. Cross the bridge and slash through the small trees on the other side so you can enter the tunnel that leads to the forest. After we enter the forest, Link will spot the young girl hanging on a tree branch from a short distance. Go up the small path until you leap off a small ledge, then head to your left. A Bokoblin will greet you as you get closer to the girl. Just strike him down with the sword, then get up on the stump so you can jump onto another ledge. Go forward until you see a log leaning onto a ledge to your left. Jump onto the log and walk across it so you can hop across the ledge. Two Bokoblins will drop down from the sky to give Link some more trouble. Just defeat them the same way you did the other Bokoblin.
By this time, the girl will awaken and then drop down to the ground to get a good look at Link's clothes before wondering where she is. Then a pirate will enter the forest, calling out to the girl who is referred to as Tetra, and feeling relieved that she is safe and sound. Tetra will now leave the forest with Link and the pirate following. As they head back toward the bridge, Link will see his sister on the other side and wave to her, but as she crosses the bridge, the big bird will come back and this time carry off Aryll in its talons. Link jumps off the cliff in a daring attempt to rescue Aryll, but Tetra grabs Link before he falls, telling him to get a hold of himself.
Back at where Tetra's ship is parked, Tetra will be astounded at Link's request to join her on her ship to go find his sister and will refuse to let him join on the grounds that it has nothing to do with her or her crew. Then the bird-like being we've seen earlier butts into the conversation, telling them that the big bird has been kidnapping young girls similar in appearance to Tetra all across the Great Sea, taking them to the Forsaken Fortress, where it makes its nest. Tetra will reluctantly agree to take Link along, but she won't do so unless he brings a shield along with him.
So let's head back to Grandma's house and climb back up to the loft where we saw the shield hanging on the wall. You'll notice that it is now gone. Climb back down and talk to Grandma, who then reveals she took the shield down so she can give it to Link. She will then become sad and heartbroken, knowing that Aryll has been kidnapped. We won't be able to do anything about her condition until later. But now that we have the shield, head back toward Tetra's ship and tell her that you're ready to ship off. A cutscene will then show the residents of Outset Island all waving at Link as he sails off with the pirate crew in order to rescue Aryll.