Shares in the firm tumbled over 8% Monday (December 6), marking a seventh straight day of declines.
That as traders totted up big falls in the value of the firm's holdings.
Chinese e-commerce titan Alibaba - SoftBank's most valuable investment - sank to record lows Monday as it announced a restructuring.
Didi Global, another top stake, has said it will delist its shares in the U.S. following pressure from Chinese regulators.
SoftBank faces trouble elsewhere too.
U.S. watchdogs have said they aim to stop its sale of chip designer Arm to Nvidia.
Only last month Chief Executive Masayoshi Son had said SoftBank shares were trading at a discount to the firm's real value.
Now they're down about a half from March highs, and at a 15-month low.
One analyst told Reuters it all adds up to a complete reversal of sentiment on SoftBank.
