Warren Buffett, through Berkshire Hathaway, significantly increased his stakes in Japan's five largest trading houses: Mitsui & Co, Mitsubishi Corp, Sumitomo Corp, Itochu, and Marubeni. Regulatory filings show substantial holdings in these firms. These companies' robust cash flows and market positions align with Buffett's investment strategy. Mitsubishi and Itochu executives view this as a sign of long-term faith.