UN leader Ban Ki-moon sets out tomorrow on a trip to Japan, where he will become one of the most senior foreign leaders to enter the Fukushima nuclear disaster zone. The tour, which will also take him to his native South Korea, is intended as a tribute to Japan after a magnitude 9.0 earthquakes and tsunami on March 11 triggered the world's worst nuclear disaster since Chernobyl 25 years ago. An estimated 21,000 people were killed or are still missing after the quake and tsunami. He will also hold meetings with Prime Minister Naoto Kan and Foreign Minister Takeaki Matsumoto on Monday.