He does think fast--and he moves fast, too, ducking and rolling out of the way of Reaper's blow. 76 is quick to put distance between the two of them, trying to countercircle, a perhaps futile attempt to anticipate what Reaper is going to do next.

Mortal enemies or not, 76 knows that their current problem is much bigger than the two of them. He doesn't want to waste time when everything here is out for their blood.

"I don't want to fight you."

It's a lie. Of course 76 wants to fight him, but he can also recognize that this might not be the time or place for their personal issues.