Reference article
Black Tufted Duck
Black Tufted Duck is a local rival who offers a race in Volcano.
Challenge
Speak to this duck in 
Volcano to enter 
Black Tufted Duck’s Race. There is no specific level requirement to enter.
Dialogue
That volcano looks like it could erupt at any second! I found this green key on the floor. You can have it if you win. Maybe it'll open that box next to the shop
Race guide
See Black Tufted Duck’s Race for the course and rewards.