Hm, since Arata doesn't know anyone outside of Shino, she's probably gonna be the only one that he'll hang with in the Magus Games. After all, youkais gotta stick together.

That being said, here's the people that he will not team up with, because he'd rather fight them instead: 
[b]Lin[/b], always nice to see muscle wizards
[b]Joulie[/b], because godly race and all
[b]Lyssa[/b], doesn't actually know her personality, so thinks that she's also a muscle wizard
[b]Sorcha[/b], now that he's fighting the pupil of the Dragonslayer, he better fight some dragons
[b]Edgar[/b], cause time stop desu
[b]Iravis[/b], fuck Crimson Avenger. Dark Knight looked cooler, and Grand Master is besto.
[b]Runik[/b], CRUSH HIS HEAD BEFORE HE BRINGS THE APOCALYPSE

Should narrow the list of people he can be teamed up with by a bunch.