Mai's story is her with support from her friend Kajun aiming to take out Relius after they hear it from him on if it's true that the school was nothing more than another of Relius' lab experiments. short answer is yes cause it was the best way to watch souls with potential through observation. basically it was like raising cattle for him.

he also told Mai she can't beat him due to having been exposed to a grimoire especially one she hasn't completed yet. what ever that means. after that she blacks out due to Relius having won the battle.