Emperor Kaika , also known as Wakayamato Nekohiko Ōbibi no Mikoto (若倭根子日子大毘毘命) in the Kojiki, and Wakayamato Nekohiko Ōbibi no Sumeramikoto (稚日本根子彦大日日天皇) in the Nihon Shoki was the ninth legendary emperor of Japan, according to the traditional order of succession. Very little is known about this Emperor due to a lack of material available for further verification and study. Kaika is known as a "legendary emperor" among historians as his actual existence is disputed. Nothing exists in the Kojiki other than his name and genealogy. Kaika's reign allegedly began in 158 BC. He had one wife and three consorts whom he fathered five children with. After his death in 98 BC, one of his sons supposedly became Emperor Sujin.

The Kojiki , also sometimes read as Furukotofumi or Furukotobumi, is an early Japanese chronicle of myths, legends, hymns, genealogies, oral traditions, and semi-historical accounts down to 641 concerning the origin of the Japanese archipelago, the kami (神), and the Japanese imperial line. It is claimed in its preface to have been composed by Ō no Yasumaro at the request of Empress Genmei in the early 8th century (711–712), and thus is usually considered to be the oldest extant literary work in Japan.