A kebumi letter was a document submitted by a lower official to a higher official. This one was signed by the Dewa-no-kami (chief) Ono no Asonchikura and the Dewa-no-suke (vice chief) Kudaraō Sanchū. Both of their names can be found in historical texts. Not only that, but since it was signed by both, we know that they were both stationed in Akita Fort. Considering when they served, this was likely written prior to Tenpyō-hōji 3 (759). It might have been that this document was submitted to the “inspector” (azechi) who governed the provinces of Dewa and Mutsu.