It has been reported that the Ka-on, written in Monnō's Makō-inkyō, reflects the Chinese Hangzhou dialect of the 18th century. However, it is questionable whether this remains true when focusing exclusively on the -mu of nasal endings. Although it is possible that Monnō had known other Chinese dialects, such as the Zhangzhou dialect, and transcribed the -m ending as -mu, there is little explanation for partly transcribing the -n ending as -mu.

This paper argues that the -mu of nasal endings in the Ka-on of Makō-inkyō derives from the articulation (hu in Chinese, or kohō in Japanese) set by Monnō in reference to the Chinese rhyme tables Yunfa-zhitu (or inpō-chokuzu in Japanese).

In particular, regarding the Ka-on -mu appearing in the divisions III and IV of charts 17 and 19, it is unlikely that there existed a unique Chinese dialect with an -n ending changed into an -m ending under the conditions in which Monnō had heard and transcribed it. This kind of -mu in the Ka-on could either be the result of accidentally confusing the articulation seishiko-sen-heikō ‘even teeth and then close mouth’ with the articulation heikō ‘close mouth’, or intentionally processing both with the same notation.