Some cultural notes on miyeok guk.
Korea is surrounded by seas on three out of four sides. The brown seaweed is plentiful and very high quality. It's mostly dried for later use.
Miyeok guk is eaten after childbirth. It's very good for the mother's health and promotes milk production. Because of this, it is traditionally served on the 100 day celebration (백일) of a birth and all subsequent birthdays. In the past, fathers-in-law would go to the market and buy the best quality miyeok available in hopes of getting a grandson. There was even a superstition that folding or breaking the seaweed would cause a difficult pregnancy.
BTW, I don't usually eat miyeok in soup. At H-Mart in Lynnwood, a wonderful cold salad is sold with vinegar, sugar, red onions and shreds of crab surimi. I don't get enough of that stuff.