It was a mixture of a writing style modeled after a translation of a classical Chinese text into Japanese and the Japanese sentences written in hiragana (Japanese syllabary characters), which was created by simplifying the Manyo-kana, an archaic form of the Japanese language.
万葉仮名を崩して生まれた平仮名による和文と、漢文の書き下しである漢文訓読体とが合流して生まれた。