There is an old fairground game called Whac-a-Mole. You whack a (fake) mole on the head and drive it down into its hole - and instantly one or more other moles pop up out of other holes. It's an excellent metaphor for humanity's inability to abolish sexual slavery.
Last week, we had the long-overdue full apology by the Japanese government for the enslavement of up to 200,000 young "comfort women" from countries conquered by Japan to provide sexual "comfort" to Japanese soldiers during World War II. Prime Minister Shinzo Abe's government finally ended decades of haggling over the scale of Japan's crime and the form of words in which it should apologise. It simply said we did it and we're sorry, and here's one billion yen ($8.5 million) to make restitution to Korea's surviving comfort women.
The apology was a bit late (the 46 surviving Korean "comfort women" are all over 80 now), but the mole was well and truly whacked. Except that in another part of the garden, another mole immediately poked his head out of the ground.
This time it was Isis (Islamic State). Reuters published captured IS documents including Fatwa No. 64, dated 29 January of last year, which purported to explain the Islamic rules on who may rape a non-Muslim female slave. Or, more precisely, who may not do so (a rather smaller number of people).
An owner may rape his female slaves, of course, but he may not rape both a mother and her daughter. Similarly, a slave-owning father and son may not both rape the same enslaved woman. And business partners who jointly own a slave may not both rape her. That would be almost incestuous.