i know in Japanese culture if you call someone by their first name its a sign to someone you are close to them in terms of relationship. like you'd call your family, close friends by first name basis. but outsiders like co-workers, on a professional lvl, aquantances you would address them by their last names then add a honorific out of respect and politeness. its a big age hierarchy rule they got there also.
I know same here, I started smiling when he called him his first name
Ditto
My biggest question here is why tf I got embarrassed when they start calling each others name lol I'm American! American ! Why am I giggling cause they said each others fist name