Tankai (1099 - 1174) was a shaso (priest who belonged to) Kumano-hongu-taisha Shrine and the 18th Kumano betto (title of an official who administered the shrines at Kumano) in the late Heian period. He was the fourth son of Chokai, the 15th Kumano Betto.
In 1137 Tankai was invested with the title of Hokyo (the third highest rank of Buddhist priests). In 1146 he was appointed the 18th Kumano Betto after serving as an official of the Hongu shrine, shuri betto (priest in charge of repairs) and Gon-betto (Deputy Betto). He had since been in office for 26 years. During his term, he served as a guide for both Emperors (and later Cloistered Emperors) Toba and Emperor Goshirakawa's imperial visits to Kumano 20 times. Also in the same period he reached the position of Hoin Gon-Daisozu (Junior Prelate with the highest priestly rank of Hoin). He raised the status of Kumano-jinja Shrines up to that of Iwashimizu Hachiman-gu Shrine.
While he served at the Kumano Hongu shrine, he founded a betsugu (shrine associated with the main shrine) named Imakumano-sha Shrine (present Tokei-jinja Shrine), thereby gaining ground to advance into Hidaka-gun.
He had close ties with the Taira clan. When the Heiji War broke out in 1159, he provided 7 armors, bows and arrows for TAIRA no Kiyomori and his followers who happened to stay in Nitagawa no Yado (also known as Tanobe no Yado) to make pilgrimage to Kumano. He advised them to return with Muneshige YUASA to Kyoto as soon as possible (based on "Gukansho" or An Interpretative History of Japan). He had a daughter who had been married to Gyokai, a master of the bow and arrow, heir of the Shingu betto family (and MINAMOTO no Tameyoshi's grandson by his married out daughter) and who had borne him two sons (Jinkai and Rinkai). He approved her remarriage to TAIRA no Tadanori.
The Kumano betto family was divided into the main Shingu betto family and the Tanabe betto family which was an offshoot (branch) family of the former. Competing with each other, both managed Kumano Sanzan (the three major shrines of Kumano).