That guy is most likely drunk as a skunk on soju. All the fights I have seen here involved very drunk middle aged or older males and looked similar with lots of ineffective flailing with little damage done. Unfortunately here in South Korea, being drunk is a legitimate defense for all kinds of bad behavior such as rape, physical violence, etc. They will probably still get punished, but often get a reduced sentence. Also paying the victim blood money, or offering to pay, if the victim declines, also usually results in a lighter punishment. The whole face saving thing from Confuscian culture has a big influence still in the South Korean justice system.
I have not seen anyone unmasked on the subway, anytime recently, here in Busan, but Seoul and Daegu were/are the hot spots. However, a lot of Koreans got complacent with mask wearing and social distancing and cases are starting to increase again, primarily in Seoul. In my area, outside on the street maybe 50-60% are still wearing masks; however, 80-90% wear them inside stores and other indoor public spaces still. If I travel to Seoul, my work requires me to quarantine for 2 weeks, as most past and current cases are happening there.