YU MYUNG-SU and his friends have been fans of Japanese culture for as long as he can remember. The 24-year-old South Korean spent years watching Japanese cartoons, films and dramas before moving last year to the southern Japanese island of Kyushu. There he has discovered new charms. “Japanese service culture is really the best,” he says.

Mr Yu’s enthusiasm is reciprocated by young Japanese; many are into K-pop, for example. BTS, a South Korean boyband of seven mop-tops of varying degrees of bleaching, who re-record all their tracks in Japanese, was the highest-selling foreign act in Japan last year. (The acronym stands for the Korean for “Bulletproof Boy Scouts”). Japanese fans snapped up 270,000 copies of one of its offerings in just one day. Meanwhile, sparse, noir-ish detective novels by Keigo Higashino, a Japanese crime writer, accounted for three of the ten best-selling works of fiction in South Korea last year. Several South Korean directors have made films based on his books.

The cultural affinity of young South Koreans and Japanese stands in stark contrast to the animosity between the two countries’ politicians. The neighbours have much in common culturally, and share strategic interests in Asia. But since establishing formal diplomatic ties in 1965, two decades after the end of Japan’s colonial rule of Korea, relations have oscillated between bad and worse.

Ties deteriorated again this month when South Korea undermined an agreement of 2015 that was supposed “finally and irreversibly” to have settled the thorniest dispute of all, over the “comfort women”—South Koreans forced during the war to work in Japanese military brothels. The government of Moon Jae-in, South Korea’s president, asked Japan for an apology (already given) and implied that Japan had not paid enough compensation by saying it would match the ¥1bn ($8m) Japan is providing to support the last surviving victims. In response, Shinzo Abe, Japan’s prime minister, suggested that he would skip the opening of the Winter Olympics in South Korea next month.

Colonial history is the main cause of the bad blood between the governments. The Japanese grumble that the South Koreans are emotional, renege on agreements and have made hostility to Japan part of their national identity. South Koreans retort that the Japanese are reluctant to face their wartime past, especially under Mr Abe, who is seen as a revisionist. There is some truth to both narratives, but the diplomatic back and forth has become petty. “I feel sold out by both,” says Lee Ok-seon, a 91-year-old former comfort woman.

America, the closest foreign ally of both countries, is frustrated too. Closer co-operation is needed to counter China, whose regional hegemony is feared by both countries, and to rein in North Korea, whose missiles threaten them both (and the American bases they host). In 2016 Japan and Korea agreed to share intelligence on North Korea. Ties are deepening between their armed forces, too. But much more could be done, says an adviser to the American armed forces in Seoul.

History matters to the young, too, but not as much as to the old. Youth in both countries have more favourable views of the other than older generations, polls say. Japanese of all ages feel more affinity with South Koreans than with Chinese; South Koreans in their 20s have warmer feelings towards the Japanese than the Chinese, unlike older people. Some are even trying to repair relations. In December young South Korean and Japanese students met in Seoul to discuss “the difference in ways of thinking” about comfort women, says Kaho Okada, a Japanese participant.

Meanwhile, cultural ties are growing. A record 7.1m South Koreans visited Japan last year, while South Korea was the most popular tourist destination for Japanese. Kim Ji-yoon of the Asan Institute for Policy Studies, a research outfit in Seoul, reckons changing attitudes herald better relations in the future. (It helps that the 31 surviving South Korean comfort women have an average age of 91.) “When I talk to my Japanese friends, we don’t argue over whose land is whose,” laughs Mr Yu.