K.
"He's my best friend. We've been buddies since we were kids."
He almost did not want to introduce Levi to her, because of the tension between them earlier. But then he realized, Levi wouldn't do that to him. Besides, he gave him an assurance that he won't betray him by messing up with K.
Levi just gave K a nod, then stirred up a friendly but awkward smile.
"Guys, this is K," he looked down and scratched his head, turning red as he thought of the next words to finish off the formal introductions. "She's... um, my girlfriend."