The main streets of Shin-Okubo — Tokyo's Koreatown — are lined with smoky barbecue restaurants and over-lit cosmetics emporiums. Staircases lead down to basement music venues and up to hidden drinking holes.

Japanese once thronged the neighborhood, which is home to many ethnic Koreans and known for its fiery food and late nights. But in recent months the crowds have thinned, replaced by anti-Korean protesters who have turned Shin-Okubo into a rough barometer of deteriorating Japan-Korea relations.

On occasional weekends this year, megaphone-wielding demonstrators have taken to the streets, telling the Koreans to "go home or die." They've threatened to "flatten this neighborhood" and build a gas chamber in its place. The Koreans say that they — and the police — have little recourse against the threats, because Japan is one of the few democracies that don't restrict hate speech.