Oni is a character from the Japanese folklore-inspired series 'Momotarō'. Oni are typically depicted as ogres or demons with immense strength and a fearsome appearance. In the story of Momotarō, they are portrayed as the antagonists who reside on Onigashima, an island where they hoard treasure and cause trouble for the people of Japan. The protagonist, Momotarō, embarks on a journey to defeat the oni, showcasing themes of bravery and the triumph of good over evil. The oni's role is central to the plot, as they serve as the primary challenge and adversary that Momotarō must overcome.