Kakashi achieves the Mangekyou Sharingan, turning to his past to do it. His past visits him while he recovers. Takes place just after Chapter Seven of Half Without Another One and "And We’ll Laugh About It". Angst, Drama, Angst, Fluff, Did I Mention Angst? Also Gore, I-5

The Sharingan’s greatest single use to him was not expanded perception, or the ability to copy others’ techniques, or even intimidation value. It’s greatest use was as camouflage. No one had to wonder why the man with a thousand jutsu kept winning; the answer was self evident.

It was also wrong.