The rank can be increased by defeating enemies or completing missions. Ranking up a class earns new Arts or Skills. Each Class has a maximum class rank of 10, at which point they may further specialize in a new class. For party members other than Cross, their class has a maximum rank of 20 and cannot be changed.
By reaching rank 10 in a class, Cross will be able to ascend to higher leveled classes. Once one of the branches has been completed (all of its classes have reached rank 10), Cross will be able to use the weapons asigned to that branch when changing to any other class.