Wikipedia
Ibaraki dōji (茨木童子 or 茨城童子 "Ibaraki child") is an oni (demon or ogre) featured in tales of the Heian era. In the tales, Ibaraki-dōji is based on Mount Ooe, and once went on a rampage in Kyoto. The "Ibaraki" in his name may refer to Ibaraki, Osaka; "dōji" means "child," but in this context is a demon offspring. Ibaraki Douji was the most important servant of Shuten-doji.
As for the birthplace, there are theories that it may be Settsu province (Mio, Ibaraki, Osaka, and Tomatsu, Amagasaki, Hyōgo) or Echigo province (Niigata, formerly Tochio, now a settlement in Karuizawa, Nanago). Ibaraki-doji had teeth since birth, and was feared for being a giant. After he became an oni, he met Shuten-doji and became his subordinate, and together they aimed for the capital.
The Shuten-doji gang was based on Mt. Ooe (said to be in Tamba province, but there are also theories that it may have been at Mt. Ooe , at the boundary between Kyoto and Kameoka. The gang ran amok in the capital, kidnapping families’ girls among other things, but they were destroyed by Minamoto no Yorimitsu and his four vassals, the Four Guardian Kings. However, Ibaraki-doji was able to escape.