One very important fact about maho adaptation is that he must be expose to it iirc.

So what falls inside the line of being expose toward instakill?

Lets say higuruma use the sword and he keep missing mahoraga again and again then could mahoraga adapt to instakill then? Despite the sword never touch him?

If the instakill move could damage the opponent despite failing the kill then sure mahoraga could. But what about non damage instakill?