Leanna couldn't defeat the other party and had to swallow her pride, allowing them to come and go freely in her own territory.
However, Diya Harut did not do anything excessive.
Because it sensed the aura of its master from Leanna and the monster followers under her command.
To be more precise, the aura of that Female Black Dragon was close to the master, suggesting a bloodline connection between them, while those monster followers were just cannon fodder tainted with the master's bloodline power.
For this reason, Diya Harut chose this place as its temporary resting ground, because in its natural understanding, this area must be one of the territories under the master's command.
If it weren't so, Diya Harut would not have given that Female Black Dragon a simple lesson; it would have killed her and taken over the territory, which would be the most likely scenario.
There is no restriction prohibiting killing between Demon Dragons and Giant Dragons.
