To obtain the Serenade to Cotera side adventure in The Legend of Zelda: Tears of the Kingdom, speak with Mastro at Dueling Peaks Stable.
For this quest, you’ll need to find Beetz. Make your way north along the main road and cross the bridge. When the road curves north, you’ll find Beetz drumming after emerging from a short tunnel near the eastern side of Lake Siela.
After speaking with Beetz, you’ll being the Honey, Bee Mine side adventure. For this quest, you’ll need to find Beetz 3 combs of courser bee honey. He’ll give you a hint that there are beehives around Kakariko Village near the huge hole. If you don’t already have some on you, make your way there to collect the honey. As a reward for handing over the honey, you’ll receive a silver rupee!
With the Honey, Bee Mine side adventure complete, return to Mastro at the Dueling Peaks Stable. To reach the Great Fairy, you must now build a boat to carry the wagon across the water to the Great Fairy Cotera. You’ll find supplies near the destroyed bridge.
Once you’ve crafted a boat, speak with Mastro and tell him to hop in then steer it to the Great Fairy. As a reward, you’ll receive a silver rupee!