A komo is a mat woven from rice straw. Wrap tofu in one and boil it, and what you get is komo-dofu.

The boiling makes the tofu develop su, countless small holes running all the way through it. The straw leaves two things behind on the surface: its smell, and the imprint of the weave, so the finished block comes out patterned like the mat that held it.

The origin given is not an elegant one. When a household made tofu there were leftovers and broken pieces, and gathering those up and binding them inside a komo was simply a way of dealing with the scraps rather than throwing them out.

But the holes turn out to matter. Simmered in dashi, a block riddled with air takes the stock in readily while still holding its shape rather than collapsing, and when you bite into it the liquid comes back out again. The smell of straw stays somewhere behind the taste the whole time you are chewing. It belongs to the Hida area, centered on Hida city and Takayama, and it appears whenever people gather to eat: at Obon, at new year, in the osechi and in the zoni, at celebrations and equally at Buddhist memorial services. A way of using up offcuts became the dish a household puts in front of guests.