[@Silver Carrot]

I think they would at least tolerate each other. I think, yeah, co-exist is the right term.

[@tipssyCalibrator]

He has to be able to see the attack coming and be able to react to it. Anything moving sufficiently fast or from an angle he doesn't anticipate, he won't be able to stop. He also can only affect the density of an object for a while before he gets tired; keeping himself hardened isn't a reasonable thing for him to do. I could also write in that in his current state, he can't decrease the density of an object while increasing the density of another object, so he has to choose between increase his own density or decrease that of an incoming object, which adds more reaction time.