I’m too busy (read: too lazy to stop playing my games) so I won’t translate the duel and all.
Basically Yuuma just argues with the sword guy about how dueling is all about light and hope and not darkness yadayada and the guy turns out to have a Numbers (No. 12). Yuuma wins and gets free card. Then the guy gets pissed and prepares to slash a statue again but Yuuma stops him by STANDING IN HIS WAY AS HE IS ABOUT TO SLASH IT. WUT. And the he gives a speech about monsters being his friends and the guy has a flashback of a time when he wasn’t an angsty idiot and actually followed his master, and drops his sword.
Granny brought Onee-chan to watch the duel to show her that Yuuma’s true potential lies in dueling and she decides to let Yuuma duel. Rokujuro gives Yuuma a shiny new deck and with that, Yuuma gains newfound confidence in winning the World Duel Carnival. Meanwhile, Astral doesn’t have ADD so he’s still unsure whether he can beat Kaito.
So yeah. Yuuma wins duel, gets new deck. From the looks of it, the plot doesn’t pick up next episode but at least it seems slightly more interesting since the preview had Astral telling Yuuma to abandon his friends.