One of the more famous pastimes of the Japanese nobility was a class of pastimes called “awase,” meaning “matchings” or “joinings.” There were uta-awase (poetry competitions), e-awase (picture comparisons), etc. With many of these, it was an actual comparison, a judging of one like item against another, the selection of the better of the two (or three or four or…) being determined by any number of factors pointing to the artistic and aesthetic sensibilities of the person or persons making the judgment.
Sometimes, however, it wasn't so much awase “matching” but literally awase “joining” that was being done. This is the case with the famous kai-awase, or shell-joining.
A full kai-awase set consists of 360 pairs of clam shells. All are about the same size (some two and a half to three inches across).
Each pair of shells bears the same image. The sources for these images are poetic, seasonal, literary, etc., and depict everything from flowers to noblemen peeking into a room to items of dance costume. The inside of the shells are first cleaned of all matter, then it is gilded and painted. Only the outside of the shell retains its natural look.
The shells are kept in a box called a kaioke, which is usually multi-tiered (or has separate trays suspended inside the single chest). Early kaioke were typically octagonal and elaborately decorated with makie or brocade-style painting, while later models were more tub-like and simply decorated and often bore the crest of the owner. Owing to the aristocratic nature of the game, by the Edo period such chests with the shells inside were commonly among the items in a wealthy or aristocratic woman's trousseau.
At right are examples of the older style (which I classify as “kuge style”) and one of the later models (which, by their popularity among the warrior aristocracy, I call “buke style”).
Playing the game of kai-awase
If the game is one using poetic texts, each shell would bear half of the poem, like the poetry card games mentioned on the karuta page. Pictured at left is a selection from a set of poetry shells. When paper playing cards came into popular use, rendering the need for the expensive shells for this simple game unnecessary, this version of the game fell by the wayside.
The left (male) shell is called the jigai (ground shell) and the right (female) shell is called the degai (out shell). One at a time, the degai is taken from the box, and its matching half is sought from amongst the jigai spread out on the floor. The winner is the person who collects most matching pairs. It sounds a bit over simplistic, however, as given enough time I can't imagine anyone not finding the matching shell. Unless, of course, the shells are spread out image down, which most explanations of the rules fail to specify.
A variation which I cannot be certain that they played, but which to me makes great sense, is a variation on the old game “Concentration.” All the shells are laid out face down, and players take turns flipping pairs, until they find a matching pair, which they can then claim. Unmatched pairs are turned back over. As with the official rules, the winner is the person with the most matching shell pairs when the game is over.
Today, in Japan, one can buy painted shells (and even “full sets”) in tourist and similar type stores. The ones you can buy today are not the real thing, however. They are real painted shells, to be sure (although some of the cheaper ones are actually applied decals!), but they are not the official 360-shell set. They are a 54-shell set, painted with two related (rather than matching) images, each one based on a chapter of the Tale of Genji.
So important is that book and its view of the Heian court that it has subsumed the real identity of the concept of kai-awase. Something I found when talking to these store clerks — and even to the management — was that they had no real awareness of what a real kai-awase set was, and were totally unable to help me in my attempts to find and buy a real full set.
These modern pairs of shells are meant to be displayed, and are sold by the pair rather than the set, and cost anywhere from ¥2,500 to ¥5,000 per pair, and even more if the art is particularly detailed and it is hand-painted rather than applied decal-work.
Kai-awase clam shells. In Japanese and English. A site for go-stones that also sells clam shells in sets for kai-awase painting.
Mikawa Workshop's Kai-awase blog. In Japanese. The Kai-awase sections of artist Fujiwara Ryoji's workshop blog. Lots of examples of shells, including shells in the process of being gilded and painted.