I'm thinking the father is a bit too trusting without evidence. Frey hasn't really done anything to prove he isn't part of a group besides say that he isn't. I mean it's nice for the story pacing that he believes Frey immediately, but you would think that he would be a bit more discerning.
It'll be explained literally right after he leaves here but there's multiple mage groups based on the 5 Heroes with Frey's being the Traumen Rings, I think. Anyways all the higher ups and powerful mages/warriors know about Demigods so him giving this information to Frey isn't a big deal - it's basics of the basics. The main reason the guy was suspect of Frey is because the Traumen Rings got nearly destroyed by a Demigod.
Almost everything about demigod becomes a retcon every time it's talked about.
You know what would be absolutely sick? If that's intentional. Demigod has control over time and space and is able to warp even the people here, albeit slightly. Lucas thought he fought against demigod alone? Retcon that because of demigod's powers. They didn't know who they were fighting against? It was one single being? Retcon and retcon.
@HayashidaYuki No, there was a blade wielder mentioned earlier, in chapter 36. He's called the Blade King Lucid. Apparently Kassajin and he were in some kind of conflict after Lucas disappeared.
Y'know, 5 vs 100 makes them so much more impressive, in the light of fighting in front of complete and overwhelming might. A single one could, and did, take out the strongest of the mages. There are dozens of similar enemies.
while i appreciate the plot exposition, it doesnt make sense that the head of a prestigious house would start blabbing about top secret stuff to a child he barely knows