Tonbokiri knew that already, in a way. But it is still amazing, and gratifying, to hear Izuminokami say it.
So he won't tease, nor say anything unnecessary. (He hopes.)

"Thank you for saying so. I take your words to heart."

And after giving a grateful smile (that Izuminokami may or may not see in his desperate attempts to hide), he turns his back towards Izuminokami once again, both giving the sword relief from being face-to-face with him, and to give him a chance to return to his task of combing his hair... once he regains his composure enough.
Tonbokiri will wait.