Ken hears the voices even before the door opens, and he shifts his body reflexively so that his torso is half-over Chikusa's own, like he's determined that anything at all that might want to get to Chikusa will have to get through him first. His eyes lock on the door, and the growl in his throat is low and quiet enough that only Chikusa will really hear it, but it throbs through his whole body with the intensity of it.

He doesn't know who Ryohei got to help them, but they're going to have to meet Ken's approval before he lets them anywhere near Chikusa.