Wu (hiragana: 𛄟, katakana: 𛄢) is a Japanese mora or a kana used to write it, though it has never been in standard use.

[2][a] Along with 𛀆 and 𛀁 (yi and ye respectively), the mora wu has no officially recognized kana, as these morae do not occur in native Japanese words; however, during the Meiji period, linguists almost unanimously agreed on the kana for yi, ye, and wu.

𛀆 and wu are thought to have never occurred as morae in Japanese, and 𛀁 was merged with え and エ.

They were phonetic symbols to fill in the blanks of the gojuon table.

Japanese people didn't separate them in normal writing.