What's going on under the kotatsu? Hmmm
Webs.
Lots and lots of webs pulling at muscles hubby never felt before. He's feeling like if his legs tripled the number of tendons, and he's not controlling any of it. She's working on two dozen muscles at the same time, making him feel purposeful clamps at the same time other muscles relax.
Or maybe just one of her foot nails scratching a flably fold under his thigh, because he hasn't been exercising lately and she knows, and he thought she hadn't noticed because he's self-conscious about it. But she did see with her peripheral eyes.
The important thing is, we don't know and it isn't us which are subjects to the semi-sadistic affections of a spidey-wife.