The Tsuchiya School artist Takechika (武親, 1827-1887) is known for having used a fair number of art names (gō, 号). From various sources, I was able to confirm at least the following 15, not counting first names and honorary titles: Issai (一斎), Gen ́ichi (玄一), Sōryūshi (蒼龍子), Takuetsudō (卓越堂), Renshinsai (錬心斎), Sensai (宣斎), Kakeisai (花鏡斎), Shima (司馬), Shimahiko (司馬彦), Keisan (馨山), Kyūraku (窮楽), Renbeiseisha (錬兵精舎), Tōma (刀馬), Shōyōken (逍遙軒), and Shōyōkyo (逍遙居).
Now I came across a fuchigashira set by Takechika on a Hozon papered tantō-koshirae, which is signed “Takechika tsukuru” (武親造, “made by Takechika”) and which bears a mysterious, and what appears to be an unrecorded gō for this artist. Before I introduce the very piece, I would like to point out that in written Japanese, an empty box (▢) acts as a placeholder for an unidentifiable/illegible characte. That is, we often see this in papers where parts of a sword’s signature are lost, e.g., due to corrosion or because a mekugi-ana was added.
As you can see in the picture above, the gō inscribed on the right side of the fuchi’s lid is ▢◯斎. Of course, the artist did not sign himself with a placeholder empty box for his own art name, so the first two “characters” of this gō have to be understood as a rebus. This brings us to the million-dollar question: How to read this art name?
Well, “box” or “square” is kaku (角) in Japanese, and a “circle” is maru (丸). So, one possibility could be that this art name reads Kakumarusai (which is, as the experts will point out, a so-called jūbako-yomi [重箱読み], a mixed Chinese and Japanese reading of a two-character combination). Well, the maru character for “circle” is gan in its Sino-Japanese reading, so maybe the proper reading of the gō is Kakugansai?
Another approach would be to pick a different Japanese character for “round” – (円) – which also reads maru, but which has the Sino-Japanese reading en. With this, the gō would read Kaku’ensai, and I personally tend towards this reading for the time being as it sounds more elegant than Kakugansai and Kakumarusai.