Buffett-backed Japan trading houses rise on Berkshire's stake boost / Shares in Japan's largest trading houses rally after Buffett's Berkshire hikes stake / Japanese Trading House Shares Set to Rise on Buffett's Stakes / Japanese trading house shares surge after latest Buffett endorsement / Nomura, Daiwa other Japan big brokers reap profits on wealth push / Buffett-backed Japan trading houses rise on high shareholder returns / Will retail investors back Japan's stock market breakthrough?