TOKYO—When SoftBank Group Corp. invested in WeWork Cos. last year, the U.S. office-rental company got more than $4.4 billion in cash. It also got a chance to win business from hundreds of companies in which SoftBank has a stake.
Today, more than a quarter of WeWork desks in Tokyo are occupied by SoftBank portfolio companies, including teams from Yahoo Japan Corp., of which SoftBank owns 43%. Ride-hailing company Uber Technologies Inc., in which SoftBank holds a 15% stake, is moving into one of WeWork’s priciest Tokyo spaces....