I can't imagine why Korean girls would wear hanbok (the traditional dresses) to school in Japan, when they don't wear them to school in Korea. Hanbok are for special occasions, and most women don't own one until well into their twenties.
And bullies? Please, they (or students like them) get bullied every day in Korean schools. The stresses placed on students in Korea (mostly to get into good high schools and universities) are just as bad as they are in Japan. Stress + school = bullies.