Investors and credit-rating firms are growing concerned about rising risks and weak controls at SoftBank Group Corp. after the Japanese conglomerate’s nearly $10 billion bailout of WeWork.

SoftBank announced late Tuesday it would spend $4.5 billion in share purchases and around $5 billion on debt financing to rescue the floundering office-share firm. SoftBank and its $100 billion Vision Fund, which is backed mainly by the company and two Middle East sovereign-wealth funds, had already poured more than $9 billion into WeWork.

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