Board Thread:Questions and Answers/@comment-118.211.8.204-20150302141811/@comment-1173941-20150324071456

Ermm... Before we make theories about how Kirito's health went back up, how about pointing out WHEN and WHERE it went back up. Because there's nothing to indicate that his health went back up after dying.

There's even this line in the novel:

As my mind sank deeper into the darkness, I could feel my body and Kayaba’s body breaking into thousands of pieces at the same time. The familiar sound of two objects being destroyed rang out and overlapped one another. This indicates that right after stabbing Kayaba, Kirito's avatar also shattered, meaning he was still considered dead by the system.