Kōgasō (光画荘) was a Japanese publisher created around 1939 by a one-time editor of Ars Camera. It published photographic magazines such as Kōga Gekkan, Gekkan Camera, Camera no Tomo and Shashin Kōgyō, and various books on photography and cameras. It became Shashin Kōgyō Shuppansha (写真工業出版社) in 1961, and still exists under that name (2008).
In 1944, Kōgasō was also distributing the Banzaikin 35mm conversion kit for 6×6 TLR cameras, made by an unknown company. The name "Banzaikin" was obviously forged after the Rolleikin. Banno Bōeki, Ōmiya Shashin-yōhin and Kinjō Shōkai were authorized dealers of the device.