Characters who are empowered by Oni heritage are typically (but not always) members of the Oni species, or their hybrid descendents on planets such as Earth with a history of isolated populations. A high incidence of metagenes (approximately 88% in the current era) has resulted in a widespread trend towards exceptional powers among the oni population, including frequent occurence of the powers of flight, electricity generation, flame breath, and exceptional size and strength.

There is strong evidence to suggest a historic population of Oni on Earth (in particular, on the Eurasian continent and its outlying island nations), including a large number of Oni and Oni-human hybrids in the afterlife of Earth. The administration of the Japanese afterlife in particular has a large number of Oni ghosts working as civil servants.

A dominant cultural trend among Oni is to identify parents and children who share the same given name by their relationship with a definite article, equivalent to Earth patronymic traditions or the use of "junior" and "senior".