Mikau made his appearance in Legend of Zelda: Majora's Mask. He was the guitarist of The Indigo-go's, a Zora rock band, and he had a romantic relationship with Lulu, the singer of the band. One day, Lulu's eggs were stolen by the Gerudo pirates. Mikau went after them to rescue the eggs, but they overpowered him and left him mortally wounded. Link discovered him floating along the shores of the Great Bay. Mikau soon passed away, but Link was able to heal his soul. What remained was the Zora Mask, which allows Link to transform into Mikau's body.
Mikau, being a Zora, was an avid swimmer. Link, in his Zora form, is also able to produce electricity as well as use his fins as boomerangs. When he takes out his ocarina, it is transformed into Mikau's guitar.