I dont think Tei is taking things for granted necessarily. I think Tei is being standoffish because he probably is angry that Shuraka lied to him and them kept him away for 10 years. As well as it is no longer a kid he feels needs protecting, its this whole ass man he doesnt know. That and by the letter and the way the king was looking at him he probably feels pressured to push Shuraka towards the princess for the sake of political ties. They are definitely not on the same page though. I think Shuraka took the vows very seriously even as a child when Tei didnt do that back then either. We are definitely going to have Shuraka chase and put pressure on Tei before we see any progress on their relationship.
I don't know how to feel about the new chapter. Maybe it's too short and I expected more of it. It does not say much about Shuraka but Tei seems to take things for granted and Shuraka hoped perhaps that Tei would reciprocate. I don't want to make much of it since we know so little about the protagonists.