Masayoshi Son, founder of SoftBank Group Corp., experienced a staggering loss of approximately $2.6 billion over two days due to a sharp decline in SoftBank shares, which fell about 14% following an unexpected interest rate hike by the Bank of Japan (BOJ). Despite this downturn, Son's net worth remains around $14 billion, significantly higher than his starting figure of $11.3 billion for the year. The decline in SoftBank's stock is compounded by a 16% drop in shares of Arm Holdings, a key asset for the company, after it failed to meet investor expectations with its sales forecast. This downturn is part of a broader trend affecting Japanese stocks, which had not seen such significant declines since 2016. The strengthening yen also poses challenges for SoftBank's international operations. Son remains the largest shareholder in SoftBank, which is valued at approximately $78 billion, although much of his stake is secured against loans.