Kasama Ware, Artist's One-of-a-Kind Demitasse Cup & Saucer

Purchased at a solo exhibition several years ago, but I don't remember the artist's name.
There is a stain-like bleed on the back, but this was present from the time of purchase, so it is likely characteristic of the material.
Never used, only displayed.

Selling to organize my collection.
I am also listing many other cups from Ginori, Okura, Copenhagen, and more, so please consider purchasing them as a set.
For set purchases, I will offer a ￥500 discount to cover shipping costs.
No box included.

Size:
Cup: Diameter 7 cm, Height 4.7 cm
Saucer: Diameter 11.5 cm