As/i/ was unified with/wi/,/e/ and/ye/ with/we/, and/o/ with/wo/ in the process of transition from Early Middle Japanese to Middle Japanese, WA-row sounds were as follows:
中古日本語から中世日本語への変化の過程で、/i/と/wi/の統合、/e/と/ye/と/we/の統合、/o/と/wo/の統合が起こったため、ワ行は下記の通りとなる。