For many years I have wanted to visit Seoul, South Korea, and this program gave me the opportunity to do so. South Korea has one of the most dynamic societies I have ever had the pleasure of experiencing. Seoul is an absolutely gorgeous city filled with a rich culture yet modern economy. On the same street, you can see modern high rises that rival any countries and traditional food stands. Speaking of food, everything is delicious and cheap. Anywhere you go in Seoul, there will always be someone making food that you can consume, either at the stands or walking. There are also plenty of places to buy things, so make sure to pack lightly.
The people in Seoul are generally very kind and respectful. They are willing to assist you if you're lost or need anything else. Foreigners are overall very welcome within South Korea.
Korean fashion is also unique in comparison to the fashion present in the USA. Every district in Korea seems to have formed its own type of clothing. Hongdae is where most people are dressed in street-wear whereas Gangnam is where most people wear name-brand clothing that costs more than my left arm.
Kookmin University is also a wonderful school, located in a very beautiful part of Seoul. There is not much to do around the school, but if you cross the street, some more traditional-style restaurants can be found if you just go down the stairs. The campus itself is very well put together. There are many trees and lovely plants not native to the USA as well as a large dragon fountain right at the entrance of the school. If you're looking for some cool spots on campus, the Student Union building has a wonderful bakery right outside the doors of the second floor (try the Squid Ink Bread, it's basically the best thing I've ever eaten).
I can't say much about the on/off-campus dorms or even the Stay4U accommodations, as I lived off-campus the entire year I studied in Korea. If you are planning on living in on-campus dorms, be aware that there is a curfew and it's quite far from where most young people like to go to hang out. If you are looking for accommodations off-campus, I would suggest looking into an AIRBNB, Seoul's Craiglist (it's not as shady as American Craigslist, but still be careful) or even on Facebook Marketplace.
Overall the city is very welcoming to those who love city life, so I encourage you to take the leap and go there. The only thing I would suggest is that you arrive in Korea with some knowledge of culture, respect, and the Korean language. You do not have to be completely fluent in Korean, but being able to read it is very helpful when getting around.
Also, if you plan on staying for a year, you should look into getting a bank card attached to your transit card, it makes traveling and purchasing things much easier. There is even a bank on Kookmin campus that can help you do this! Good luck and have fun!