Tsunade's behavior was probably the result of hearing too much gossip and letting emotion outweigh reason. Unable to make sense of things for the moment, she had rashly come to question Karn.
From Tsunade, Karn could tell that someone in Konoha bore him ill will again. This attempt was more sophisticated, though. Sowing discord was better than rashly sending ANBU to his door to kill him, and when it came to their affiliations, people from the same village had a natural advantage in their relationships.
Acting in a personal capacity, Tsunade secured a shipment of medicine from Karn, at a lower price than ever before, which left her feeling somewhat ashamed.
After returning, she still felt awkward around Karn. She hurriedly handed him the finished medicines and formulas for three terminal illnesses that she had prepared beforehand, then returned to her room without saying anything else.
Nawaki had long since gone to bed. These days, he either went on missions or was worked like a dog by Orochimaru. After learning about the New Extremis Virus's regenerative abilities, Orochimaru never held back with Nawaki, frequently employing all manner of vicious methods and even snake venom.
That time, Nawaki paid for his carelessness with three minutes of convulsions. Ever since, he had been extremely careful about everything and could only rest at ease once he returned home.
"Boss, are you done talking?"
Just as Karn was about to leave, Kushina quietly poked her head out of the hall by the kitchen and whispered to him.
"Just about. Kushina, what are you doing...?"
Kushina glanced around as she said, "I just remembered that I haven't asked how your sealing jutsu studies are going. If you've learned it, would you like to learn something more advanced?"
Tempted by the offer, Karn said, "Can I?