>>192823
If I remember correctly, the pronunciation of ふ is also an example of debuccalization. In Early Middle Japanese, what is /h/ in Modern Japanese was pronounced /p/. /p/ then lenited (softened) to /f/, which then debuccalized to /h/ everywhere except before /ɯ/, which is why ふ (/fɯ/) is still pronounced with an oral consonant.

In Japanese compound words, there is a rule known as rendaku, which is the voicing of the initial consonants in the second element of the compound word. For instance, the /k/ in 心 (/ko.ko.ɾo/) becomes a /g/ in the compound 女心 (/on.na.go.ko.ɾo/). In words that begin with an initial /h/ such as 人 (/hi.to/), rendaku does not change it to its proper voiced equivalent, which would be /ɦ/, but instead to /b/. An example is 人々 (hi.to.bi.to). This shows us that what is /h/ now historically acted as /p/, because /b/ is in fact the voiced equivalent of /p/.