S01E21: Naraku's True Identity Unveiled

Kagome returns to the shrine in the middle of her date with Hojo. She senses the presence of the Shikon Jewel shards and returns to feudal Japan. Naraku reveals that fifty years ago, Onigumo was in love with Kikyo. The demons that were drawn to Onigumo by his malice devoured Onigumo, and the demon Naraku was born.