Well, instead of manipulating the physical characteristics of the blade, I was thinking about splitting the blade into smaller fragments - of course, the smaller the fragments, the weaker they are. The fragments could be controlled by him as long as he holds the hilt of the blade/has at least one fragment of it still attached to the hilt.

 I see that this ability can be of more help to the team - and maybe even more fitting for Michiko, partially due to his obsession ( and my liking ) of maths - but that can be explained IC.

Ok, so I posted. I know it might not be great and I do aplogize if I misread anything in your post, but I am tired as hell. I will make any and all necessary Corrections to my post in the morning. After all, I am a Corrector.