The new U.S. ambassador to Japan, Rahm Emanuel, arrived in Japan on Sunday, filling a key post that has been vacant for more than two years and taking on the crucial task of enhancing their countries' alliance amid China's growing assertiveness in the region.The 62-year-old former top aide to former President Barack Obama is known for his close ties with President Joe Biden.Emanuel gained the trust of Biden when he was White House chief of staff from 2009 to 2010 for Obama, whom Biden served as vice president.After his arrival in Japan, Emanuel tweeted that he and his wife are "excited to h…READ FULL ARTICLE