The Goron kids ask you to intervene at YunoboCo HQ, and you end up having to fight a boss battle.
Clearly Not Himself Yunobo
Yunobo will stomp several times, then start spinning. Eventually he will dash forward toward you, but if you keep moving and keep your distance, you can avoid letting him hit you.
If he dashes into a solid wall, he will be stunned for a moment. Hit him while he is stunned, and his mask will partly shatter.
As the battle goes on, there will be a shorter delay before Yunobo dashes forward.
After you hit him three times, his mask will completely shatter, and the battle will end.