Among the postcards and other materials in the Iwaya family collection, there are 22 postcards from KUBOTA Beisai to IWAYA Sazanami, dating from 1901 to around 1918. This paper examines the relationship between Beisai and Sazanami by examining the 22 postcards and comparing them with the diaries and other related documents from that period. It has become clear that the two knew each other before travelling to Europe, and that they were close, not only through their involvement in children's literature and children's magazines, but also through their interactions in France in 1901, their haiku and picture postcard clubs, and their activities at the Mitsukoshi department stores.