Joe is lot younger and more childish than what I presumed by the previous chapter. Based on the characteristics shown (doesn't care about his comrades, treats battle like a game, anime battle junkie personality), I'd predict he loses here to Ritsu and then attaches to Ritsu as sort of little brother type character to learn from him while redeeming his ways and learning to serve Ars-sama, maybe with the promise of getting to battle stronger enemies in the future.
Of course we have to give Ars-sama screen time as well, so now that he solved the castle problem with his brilliant stratagem of attacking from the other direction and his brilliant commands of "just take the castle over" he will show up to the duel with Joe and either give Ritsu a boost thanks to their master-servant relationship (perhaps he gets in danger) that lets him win or perhaps to show Joe the error of his ways as he gets overpowered by the "weakling" reinforcements Ars brings in in a sort of ironic twist for Joe.