Mimisenri

is a demon who has very good hearing, and tells Naraku the location of the final shard of the Shikon Jewel.

It is said that Mimisenri can hear everything that happens in the world due to his extraordinary hearing, and he has wisdom much beyond his years due to this. When Naraku appears before Mimisenri, the large eared demon asks if Naraku plans to absorb him into his body so that he can hear things extraordinarily well too, but Naraku replies he has no interest in absorbing a filthy body such as his. Mimisenri hears Naraku coming from "four miles away" and asks if he's seeking information on the Shikon shards, hearing from numerous demons that Naraku has gathered most of them. Naraku corrects him and says there is only one shard left he cannot find, so Mimsenri strains his ears, listening for rumors on the jewel, and tells Naraku that the final shard is in the Borderland between this world and the afterlife. This is how the hunt for the final shard begins.

Trivia

 * For some strange reason, Mimisenri appears along with Naraku and his minions in the opening "One day, one dream", despite only having a minor connection to him.