Kris as a heir of heart. The argument for knight is that they sort of "serve" the player (the self). But I think the amount they are controlled by the soul could indicate heir. Our presence is thrust upon them suddenly. Like an inheritance. As the soul/player we actively provide the "self" to Kris by making internal decisions about them (like personality/demeanor). If we interpret heir as a restoration class, then there's even more evidence, since at the end of each chapter so far, Kris restores the light world by closing a fountain. Also, you know who else is blue and the main character? John egbert. A heir. Case closed.