South and North Korea displayed rare unity on the U.N. Security Council Wednesday, as they fiercely condemned Japan for history "distortions."    The two Koreas, backed by China, said that Japan's conservative leadership is fully responsible for escalating tensions in Northeast Asia over history and territorial issues. Amb. Oh Joon, South Korea's permanent representative to the U.N., accused Japanese leaders of having a "distorted view of what happened during the time of imperialism."    He was speaking at the U.N. Security Council's "open debate" session with the theme of "War, its Lessons, and the Search for a Permanent Peace."    His remarks reflected uproar in South Korea over Japanese Prime Minister Shinzo Abe's visit to the Yasukuni Shrine in December and his administration's decision to teach students that Dokdo, a pair of rocky outcroppings in the East Sea, is part of its territory.