Mount Kajiiki was a volcano in Japan.
Long ago, an ancient fighting master developed a fighting art known as Kiba no hoko, which proved too deadly to teach. As a result, he hid the only copy of the art's technique in one of the slopes of Mount Kajiiki. He told only his eldest son, and the family has kept the secret for generations.
Five hundred years later, Kyodai Ken obtained the location of the instructions for Kiba no hoko from Yoru, the last living descendent of the fighting master. Once he mastered the art's fatal o-nemuri touch, he lured Batman to Mount Kajiiki for their final match.
At the volcano, Bruce and Kyodai fought, despite how it was erupting quickly. When a flow of lava had separated them, Kyodai was stranded on a small rock. Bruce tried to save him, but as a gesture of honor, Kyodai refused and was likely killed by the volcano.