Although he was only doing what Madam Irene had said, the moment Master Luca found out about his intention to seduce Ayana, the poor man was dead. And the woman did not even lift her finger to say anything to save the man. The last thing people heard about Sebastian was that he moved somewhere far away.
Some people believe that he was only transferred to a faraway place, but Nicolas has a hunch that the man was tortured and maybe dead. People were curious about what he had done and the result in that miserable situation, but it's just about that. If they knew what he had done, they would start to ignore him. Everything was clearly his mistake. He was the one to seduce the general's wife.
So the moment Irene appeared and brought Madam Ayana back and shove two simple yet deadly decisions on his face, Nicolas was clear that he better offended Irene than Luca. He has a hint that Irene would gladly give him a quick death, unlike Luca.