TOKYO— SoftBank Group said a decline in the value of many holdings in its investment portfolio sent its profit lower during the latest quarter, showing that headwinds are rising for the world’s biggest tech investor.

The Japanese conglomerate, best known for its $100bn Vision Fund, said net profit was ¥761.5bn, equivalent to $6.9bn, for the quarter ended June. That was lower than the year-ago figure and a fraction of the record-setting January-March quarter, when the company rode booming stock markets to multibillion-dollar gains on its investments.