Big fucking lie. Look at the guidelines (.pdf file in German), they don't give a recommendation on asking anyone to leave an event venue. What they state is that people from designated high risk areas may increase the overall risk of the event. Japan is not one of the designated areas, as the institute only lists China, Italy, Iran and South Korea. This is a weak attempt at covering up the racist behaviour of the security service they hired. According to the MDR (eastern German broadcasting company) it has happened during a youth match, too.