Thatcs sort of the looming theme in this manga. Anywhere he goes or comes back too could have changed dramatically for better or worse. zweeden getting a mountain range might suddenly become a neutral financial hub of the continent or might attack the elves in a few generations.
Who can tell...
I'm going with either a mix of 1 and 2, a student selling his craft to the gov't or straight up the gov't not wanting his secrets to fall into anyone else's hands
It does things to me, so it checks out.
Yura being immediately adorable and accepted into the family is so great, as is the chill aspect of this chapter.