Was reading through the story again, but I got a little sidetracked trying to figure out where they are going with Magatsu. It somehow seems like he's set up to be destroyed, but the sword that was his gift hasn't disappeared like should happen with any isekai'ed person that dies. This assumes that Uncle kept his since he got back somehow that didn't involved death. With Uncle implying that his horrible deeds may have been overstated, he unexpectedly might hang around for a while.
They also mention the Kofun era and how little information there is on it. Interestingly enough, some of that information comes from China, since sometime in the mid 200s AD, the Chinese emperor of the Wei dynasty met with a group claiming to be from the islands that are now Japan. Wa, I believe? They had a queen at the time, who is rather well known now by the name of Himiko. So the time period is pretty interesting, even if it doesn't mean a thing yet.