Lingering resentment over the treatment of Korean sex slaves during World War II — and the perception that Japan has failed to show remorse for its actions — help explain outbursts of Korean anger more than 70 years after the war's end. "Historical grievances in Korea…simmer on and on until every once in a while they boil over," said Jeff Kingston of Temple University, Japan Campus. "Tokyo is living in a dream world if it believes that these matters are resolved and not worth addressing."