For SoftBank Group Corp., $100 billion (¥11 trillion) isn't enough. The conglomerate, which has reshaped the technology startup landscape with its Saudi-backed Vision Fund, is in talks with investors to add as much as $15 billion more to its already massive fund, according to people familiar with the discussions.

In about two years the Vision Fund has invested more than $70 billion in tech companies. SoftBank wants to continue its deal spree while leaving enough assets in reserve to continue buying shares in companies it currently backs. Later, it plans to undergo an even more ambitious effort to assemble a second Vision Fund, said the people, who asked not to be identified because the deliberations are private.

SoftBank has weighed a variety of ways to pump more cash into the original Vision Fund. Proposals include raising more capital, persuading state-backed investors in Saudi Arabia and Abu Dhabi to waive their rights to debt repayments or taking out more bank loans, said the people. Terms of the fundraising have yet to be finalized, and there's no certainty a deal will come together, one of the people said.