The Illfang Boss battle concludes with Kirito getting the Coat of Midnight and invited you to his party, unfortunately.

Now, Kirito is sitting with Sachi and is speaking to her, as you listen from the bridge.

"You're looking at a new Kirito! One that shows the compassion people deserve." He said with a smirk.

"Well, i guess I'm tougher than I thought- AHHH!" He passes out. You carry him back to the base begrudgingly.

He wakes up and looks at you. "You... ass. I was working on that girl."