The story of Momotaro may be related to the old believes of the onmyodo 陰陽道 Yin-Yang Worldview. The direction of bad influence, kimon, is in the ushi-tora (bull tiger) direction. So one of the demons Momotaro is fighting has horns and the other wears a tiger skin.
And the Monkey, Dog and Pheasant are animals in the zodiac, in the opposite heavenly direction from the kimon 鬼門 . Another source for the oni's image is a concept from China and Onmyōdō. The northeast direction was once termed the kimon (鬼門, "demon gate"), and was considered an unlucky direction through which evil spirits passed. Based on the assignment of the twelve zodiac animals to the cardinal directions, the kimon was also known as the ushitora (丑寅), or "Ox Tiger" direction, and the oni's bovine horns and cat-like fangs, claws, and tiger-skin loincloth developed as a visual depiction of this term.