Masayoshi Son said he would begin to make personal investments alongside SoftBank Group Corp.'s Vision Fund, a controversial step that could lead to conflicts of interest as his company backs technology startups. The Japanese billionaire made the disclosure as his company reported earnings, explaining he will begin to co-invest in Vision Fund 2, an investment vehicle where SoftBank has been the sole source of capital. Son can invest up to $2.6 billion and will own 17.25% of the equity. He will have a similar arrangement with SoftBank's Latin America fund. Business leaders tend to avoid mixing their personal financial interests with corporate responsibilities.