What would happen if I wave a Soviet flag in Japan?

https://images.app.goo.gl/Jmw6J628Gk9LH8H28

I had a Russian friend in my school in Tokyo. He was a typical care free guy, who didn’t worry much about anything. So, I met him around 11th of May. Knowing that Russians love 9th of May holiday, Victory Day, I casually asked him how he celebrated it. The guy looked at me, smiled and said: “I’ve got kicked out of my apartment.”