Absolutely agreed. His words and his face made it seem like he rather said "alright you morons, are we playing dumb on it or we doing something as real men?" That was not approval. That was a big warning
Did you see the face her mom made in the previous chapter (I think it was 19) when Sou didn't want to approach him because she was awkward?? That "yare yare" look on her face. Of course she knows. She was the first one to realize if you ask me
First. Which is legal in Japan, but is on the decline. It used to be that whether or not cousin marriage was considered incestuous was a regional thing, at least according to this post.