Onigumo

Onigumo was the original human identity of the powerful demon and major antagonist Naraku

Muso
When Naraku removed his human heart, he also removed Onigumo's soul in the process. Much later, Muso finally remembers about his past as a bandit and of his time with Kikyo within the cave.

Final Death
In one of Naraku's final moments he recalled that Kagome said the the jewel did not grant his real wish. Naraku recalls that what he really wished for was Kikyo's love, but it seemed that it was not granted to him. Before Kagome's arrow pierced the jewel, Naraku comments that he won't be able to go where Kikyo has gone. It is presumed that Onigumo's emotions have somehow surfaced within Naraku as he recalled his true wish.

Trivia

 * Even though Naraku was the ruling personality of Onigumo's former body, Naraku seemed to retained some of Onigumo's memories, and desires as well: The Shikon Jewel, and the priestess Kikyo.