Seaweed soup has been loved by Koreans for a long time. Because it's easy to make and perfect match for Koreans who consume cooked rice as a staple food. It contains rich calcium and iodine which is good for mother who just delivered baby and to growing children.
Eating seaweed soup on one's birthday is our culture. Korean people would ask 'is today anyone's birthday?' when you serve seaweed soup to him.
So, If you have any Korean friend, ask "have you eaten mi-yuk guk?" on his birthday. He will appreciate :))