Board Thread:Naruto Discussions/@comment-24165784-20151108230957/@comment-26537507-20151115200529

If the soul's already been eaten then it would be too late to activate it. If Izanagi had been activated any time before that, then the user should be safe. So as if they activated it and their soul got eaten, theoretically they could overwrite that. As for the user of Shiki Fūjin, Izanagi has only ever benefitted the person using it. If the technique has finished and the Shinigami has eaten their soul, then they're dead. If the Shinigami was in the process of dragging the Izanagi user's soul out, then theoretically they still have a chance.