Since Han Fei and Xia Xiaochan had come to the Merman Royal Family, they were going to let Xia Xiaochan be sealed in the Merman Royal Family. In this way, at least they wouldn't have a conflict with the Merman Royal Family.
As for whether Han Fei's words were credible or not in the eyes of Xia Hongzhu and the others, it would be known when they sealed Xia Xiaochan.
If it was really a Monarch taking action, how could the commotion be small?
If Han Fei did something to harm Xia Xiaochan in the territory of the Merman Royal Family, the three Sky Openers of the Merman Royal Family wouldn't give Han Fei a chance to leave today.
Most importantly, Han Fei had no reason to do anything to Xia Xiaochan. Since he had opened the sky, his bloodline level was not low.
