It is considered that a sound [p] existed in the Japanese language in the pre-literature period, but it turned into a fricative consonant [ɸ] as early as the end of Old Japanese and further changed into a sound [h] in Early Modern Japanese.
文献以前の日本語には[p]音が存在していたと考えられているが、これが上代日本語末期までには既に摩擦音[ɸ]となり、さらに近代日本語において[h]音へと変化して現在に至る。