Visiting a Special Shop
The quest is unlocked after completing The Future of Hyrule scenario.
"A boy who heard that the Skull Lake rumors were true wants to shop at the Fang and Bone. But he's been unable to get monster parts to trade. Help the boy out—get him some."
"With monster parts in hand, the boy got to shop at the Fang and Bone. It seems he really just wanted the fun of going there, however, so he gave you what he bought for free!"