Grigori being mad was a bit outside of his expectation. But he understood where the Vampire lord came from.
His words could be easilyy misunderstood as a threat, while what he gave to Grigori was a mere warning.
"Even if you're the Ruler with massive strength, I won't allow you to threaten me or my territory."
From this, however, he learned a little about Grigori's personality. The Vampire lord's subordinates outside also seemed to respect him greatly; at the same time, they also feared him.
The Vampire lord could be described as a mafia leader with a bigger gun in his pants.
"That's not my intention," Kai replied calmly, looking straight into Grigori's eyes, not wavering a little.
So what if the Vampire lord was angry and looked scary? In his life, Kai had always dealt with a scary old man with an anger issue. Without him noticing, as time passed, his mind was trained, and he built immunity to fear.