Asuka VS Big Brother! It's Battle for Certain Love! Urusei Yatsura : Season 1 Episode 206

Asuka will not stop flirting with her brother, so her mother makes a desperate wager with her: if he defeats in Asuka in combat, Asuka must give up on marrying him. Unfortunately, their respective martial abilities mean she's almost guaranteed a victory. Lum's help is employed. It gets weird.