Link can box Blaino at his gym in North Horon. After Link wins back Ricky's Gloves by defeating Blaino once, he can pay 10 Rupees to challenge Blaino again, and has the chance to win 30 Rupees if he knocks him out of the ring. However, if he cheats by equipping any of his items, no matter which; Link is disqualified and is forced to pay 20 Rupees for all subsequent challenges.
During Link's quest, he meets a Goron in Death Mountain's Hot Spring. This Goron explains how sumo is boring and that the younger generation needs a new sport. The boxing match in the ending credits seems to be a direct response to this comment.