Shares plunged ¥354 to ¥4,741 on Wednesday as SoftBank got swept up in the worst global semiconductor selloff of 2026, a five-day rout that has now erased more than $1.3 trillion in market value from the world's top 20 chip stocks. In total, 20 of the world's most valuable chip stocks lost $1.3 trillion since market close on Friday, according to a CNBC analysis using FactSet data. SoftBank has shed roughly 20% since July 22, when it traded above ¥5,700 — a punishing streak that tests the thesis behind Japan's most aggressive AI conglomerate.

  • The Selloff Isn't About Bad Earnings — It's About Shaken Confidence. "This decline appears to be driven largely by sentiment rather than fundamentals," said Morningstar's chief equity strategist Michael Field. "Simply put, it's loss of confidence."

Forrester's Charlie Dai said AI infrastructure spending may be "peaking faster than expected." For SoftBank, which doesn't make chips itself, the fear is indirect but potent: if the AI buildout slows, demand for Arm's chip designs and the value of its OpenAI stake both deflate.

  • SoftBank's Fortune Rides on Two Giant, Illiquid Bets. SoftBank owns an 86.39% stake in Arm through the Vision Fund.

By October, SoftBank's total commitment to the ChatGPT maker is expected to hit approximately $65 billion. Together, Arm and OpenAI account for the vast majority of SoftBank's asset value. That concentration means any wobble in AI sentiment hits SoftBank harder than a diversified tech investor — and makes the stock behave like a leveraged bet on a single sector.

  • Debt and Leverage Add Extra Pressure. SoftBank's heavily debt-fueled model continues to accumulate fixed repayment pressures. SoftBank signed a $40 billion bridge loan last March, and S&P has already downgraded its credit rating outlook to "negative."

It was reported that SoftBank took out an $8.5 billion margin loan on its Arm stock, with the capacity to tap another $11.5 billion. If Arm shares keep falling, that margin loan — essentially borrowing against its biggest asset — could force uncomfortable choices.

  • CEO Son's Grand Vision Hasn't Calmed the Market. At SoftBank World 2026 on July 14, Son projected global AI infrastructure will require $5 trillion in annual investment by 2040 and called bubble fears "absurd." The remarks appeared to prompt profit-taking, as investors noted Son offered no clear methodology behind his figures.

A UBS basket of shares geared to AI spending is now trailing stocks deemed at risk of AI disruption by a record 42 percentage points — a stark measure of how fast the crowd has turned. Until SoftBank can show near-term cash returns, not just long-horizon promises, its stock will remain hostage to the mood of a market that is no longer willing to pay up on faith alone.