Having gone back in time and essentially helping save Hyrule a second time, Link rode through the Lost Woods on Epona. As he rode through the foggy terrain, he was ambushed by Skull Kid and his pair of fairies. After Link was knocked off Epona, the Skull Kid took his ocarina and began playing it. As soon as Link got back on his feet, Skull Kid took off with Epona and the ocarina. Link gave chase until he fell down a hole.
Link fell into a huge void. He was surrounded by colorful faces, but was falling too fast to make any of them out. Eventually, Link landed safely on a flower in front of Skull Kid and his fairy partners.
"What with that stupid horse of yours?" Skull Kid asked, "It doesn't listen to a word that's said to it! There's no point in riding a thing like that, so I did you a favor and got rid of it! Tee hee... Oh boo hoo. Why the sad face? I just thought I'd have a little fun with you."
Skull Kid shook his head and radiated a strange energy. Link began halucinating foxes. Multi-tailed foxes. Keatons. They were surrounding him and then he was being chased by a massive keaton.
When the halucinations ended, Link was horrified to find he had become a keaton. Skullkid laughed at Link's misfortune as he slowly floated toward the exit and closed the door. Link quickly followed him through the door and quickly wound up in a dark stone room with unfamiliar machinery. Exploring the room further, Link ran into a smiling man carrying various masks.
"You've met a terrible fate, haven't you?" the man told Link, "I own the Happy Mask Shop. I travel far and wide in search for masks. During my travels, a very important mask was stolen from me by an imp in the woods. So here I am at a loss... And now I've found you. Now don't think me rude, but I have been following you... For I know of a way to return to your former self. If you can get back the precious item that was stolen from you, I will return you back to normal. In exchange, all I ask is that you also get back my precious mask that imp stole from me. What? Is that not a simple task? Why, to someone like you, it should be by no means be a difficult task. Except... The one thing is... I'm a very busy fellow... And I must leave this place in three days. How grateful I would be if you could bring it back to me before my time here is up. But, yes... You'll do fine. I see you are young and have tremendous courage. I'm sure you'll find it right away. Well then, I am counting on you..."
Link wondered what he could do. He was in an unfamiliar body that rendered his equipment useless. He was just a fox now. A weird fox with multiple tails and...
Link realized he had the body of a keaton vixen. Keatons were known for having the ability to disguise themselves, but Link had no idea how that was supposed to work. Still, he... she had a job to do and would just have to figure it out. She decided to open the door and find some way to get her horse and ocarina back.
Leaving the room, Link found herself in front of a clock tower inside a small town. The workers in front of her didn't seem to notice her as she explored the town, probably an ability of keatons she was unfamiliar with. She managed to run past a guard unnoticed and found herself in an open field.
For hours, she explored her surroundings. There was a swamp to the south, a desert to the east, an ocean to the west, and a snowy mountain to the north. Most of these areas were blocked off, so Link headed to the swamp.
Link didn't know what she expected. It was wet. It was hot and humid. She feared if there was any more huditity, she'd drown where she stood. There was pretty much nothing she could do there at that point. It looked like her only real path forward was through the water, but the water didn't look safe to swim in. With no other option available, she turned around and returned to the field.
Link decided to return to the town as night fell. When she finally looked up at the moon, she noticed it was significantly closer than usual. She also saw Skull Kid floating above the clock tower.
Link had her target. She just needed a way to get to the top of that tower to confront the thief and get her ocarina back.