Abihiko is a legendary person in Chusei Nihongi (A set of medieval Japanese mythologies). Abihiko is also known as Abio.
In "Soga Monogatari" (the tale of Soga), which was established during the Kamakura through Muromachi periods, Abihiko is described as Demon King Abi who was exiled from the ancestral Ezo (northerners). Abihiko is supposed to be the older brother of Nagasunehiko, and some say that Abihiko and Nagasunehiko made an escape to Hirosaki in Aomori Prefecture, and others say that Abihiko was singly exiled to the Tsugaru region.
However, neither "Kojiki" (The Records of Ancient Matters) nor "Nihonshoki" (Chronicles of Japan) does not mention about Abihiko. Abihiko is generally regarded as a fictious person, but a theory says that Abihiko is actually the same person as Nagasunehiko.