The tenth installment of the series introducing Japanese documents preserved with Bronisław Piłsudski’s archives in the Scientific Library of the PAAS and the PAS in Cracow focuses on a postcard message written in refined cursive script style labeled草書体 sōshotai (not necessarily correctly translated as ‘grass script’) quite difficult to decipher. When deciphered, the message seemed easy to translate but a reconstruction of possible sequence of events proved necessary. The author of the message and the calligraphy was Motonaga Murao, a high-ranking state servant, formerly working in the Hokkaido Development (~ Colonization) Agency (~Commission) and Hokkaido historian, educator, and author of several fundamental publications on the island and its development, works on the Ainu included. The message itself is doubtlessly a response to Piłsudski’s apparent request to meet – again doubtlessly – to exchange the knowledge and experience concerning the people of interest to both: the Ainu. The installment provides also information on Murao and his accomplishments.