"I promised my dongsaeng I'll treat her for dinner if she did well on her test."
"Dongsaeng, make me a cup of coffee."
(Although the above statement is a command, 'dongsaeng' acts as a form of endearment like 'little
brother' or 'little
sister'. In other
words: "Lil' bro, how about a cup of coffee for your big bro?")