so the other guy calls his friend's mom "mom" as well? I didn't realize they were brothers, unless he's being a weird one as well
I was just about to make a comment about this, and your post shows how... Shallow? This series is.
Sou is not his biological brother. That has been stated explicitly before. The mother was saying act like his older brother.
But that leads me to my point. We get like...zero explanation of Sou's past. For an explicitly main character, we see very little of who he is.
And the there was the teacher's statement about the airport. Like, it seems like the author is just doing whatever without deeper thought.
Which I've complained about before, but it's still weird.