Ibaraki Doji is an Oni featured in many stories in the Heian period. In the tales, Ibaraki Doji is based in Mount Ooe and went on a rampage in Kyoto together with Shuten-Doji. The "Ibaraki" may refer to Ibaraki, Osaka; "Doji" literally means "child," but in this context is a demon offspring. He is 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.