Hirohito did, eventually, end the war in the Pacific -- it was his decision to surrender, and he essentially stepped in and overruled his cabinet when it deadlocked over the decision -- but he was in many ways a symbolic ruler, and did not necessarily participate in the day-to-day running of the country. For what happened at the end of the war (it's still not clear whether the atomic bombings of Japan or the Soviet invasion of Manchuria tipped the Japanese into surrender), see more in this excellent older thread: https://www.reddit.com/r/AskHistorians/comments/1y5g5j/what_happened_to_the_japanese_politicalmilitary/