The aim of this article is to emphasize the necessity for further investigation into the relationship between Sino-Japanese and Yamato, and to present a couple of topics on the historical phonology of Japanese. One of the main questions that deserves to be challenged is how the indigenous structure extended to SJ word formation, such as geminations, of which the earlier stage can be hardly attested by historical records. Another topic concerns vowel coalescence. The interesting interaction between SJ word types and Yamato accounts for these sound changes.
