After listening to what Avila had to say, Yuki instantly got flashbacks of his battle with the 3 kingdoms that had joined forces all for the purpose of defeating Yuki. Although they had failed to kill Yuki themselves, they had managed to ruin Yuki's life. Not only did he have to lose the only family which he ever had in the form of Elpis and Marcell, Yuki couldn't also form any real friendships with anyone since he would be known throughout the entire world as a murder. Although Yuki never wanted to kill everyone in the army of the 3 kingdoms, he had no other choice due to them constantly chasing him.
It was a bit ironic that the person who had ruined Yuki's life, that being Scar who had set up everything for the war against a single man, had become friends with Yuki himself and was now complaining that their friendship was drifting apart.