[Mikado just holds on stubbornly, wincing a bit. But since he's holding her close enough, she can headbutt hard, but there's no momentum behind it.]

Th-there's a limit to cheating. I-if you can get free in five m-minutes you win. I-if not, i-it's my w-win.

[Why not? He can make up rules as well as she can. And he has his hands locked together behind her back, so he may not be the strongest, but he's confident in his hold on her.]