Kyo Kara Maoh! - Season 1 Episode 2

While attending a dinner party that the former Queen is holding, Wolfram insults Yuri's mother by saying she is dirty human and Yuri reacts to the insult by slapping Wolfram across the left cheek. From everyone's weird reaction to the slap he finds out that this is actually how the nobles of the Demon Kingdom propose. Wolfram then throws his silverware on the floor to challenge Yuri to a duel to contest the engagement and Yuri unknowingly accepts by picking up a knife. Yuri is allowed to choose how they fight the duel and so he decides they should fight through a sumo match.