Massive plothole
Throughout the show, we're told that Naraku is incapable of hurting/killing Kikyo because Onigumo's heart still lives within himself. How was he able of deadly wounding Kikyo 50 years in the past?
shareDuring the Muso episodes it's stated that as soon as Onigumo sold his soul, the demons took control of his body, 'locking' him away inside. How Onigumo was somehow able to over come the demons and have his conscious effect Naraku 50 years later is another question, and possibly an even bigger plothole.
"We stopped checking for monsters under our bed when we realized they were inside us"