On the way to Ryoma's match, Atobe and Sanada decided to finish the undecided match between them (the one where Atobe perfected his Koori no Sekai move and Yukimura stopped it before Sanada lost) and to be funny they decided to settle it with JanKenPon (rock paper scissors) using their catchphrases XD
I loved Kazuki Kato, but this new Atobe is pretty awesome, too. XD ...He's got a way deeper voice for some reason... fffft. Jan-ken-pon. I can see this happening in the actual manga... (Konomi's actually made it canon that Sanada's unintentionally dorky.)