Sompo logo is seen in this illustration taken February 3, 2025. REUTERS/Dado Ruvic/Illustration

By Pritam Biswas, Anton Bridge and Kiyoshi Takenaka

TOKYO (Reuters) -Sompo Holdings said on Wednesday that it would acquire New York-listed Aspen Insurance Holdings for about $3.5 billion, joining a number of Japanese financial firms that are investing in overseas assets to drive growth.

Sompo has offered $37.50 for each share of the U.S. firm, which is majority-owned by Apollo Capital Management, representing a 35.6% premium to Aspen's unaffected share price. Aspen shares rose 13% to $36.40 in morning trading.

"While we think the company is worth more intrinsically, it is hard for us to imagine another bidder emerging," Citigroup said in a note.

Dwindling growth in the domestic financial market has prompted Japanese companies, including insurers, brokerages and banks, to explore overseas options.

Some of the recent deals include Nippon Life Insurance buying Resolution Life Group Holdings for about $8.2 billion and Nomura's decision to acquire Macquarie Group's U.S. and European public asset management businesses for $1.8 billion.

"The domestic pond is over-fished with an aging population and decades of thin yields, so they're buying durable, dollar-denominated cash flows and fee businesses abroad," said Michael Ashley Schulman, partner and CIO at Running Point Capital.

Sompo plans to integrate Aspen's operations with its overseas insurance business to strengthen its presence in major markets, including the Americas and the UK.

"Strategic acquisitions have been a key part of our growth plan to build a robust and diversified global P&C (property and casualty) platform, and Aspen represents an excellent opportunity at the right time in the market cycle," Sompo P&C CEO James Shea said.

Apollo, which holds an 82% stake in Aspen Insurance, took the company public earlier this year after taking it private in 2019 for $2.6 billion. The company's valuation hit a little over $3 billion on its debut day.

Aspen's acquisition will be financed entirely through Sompo's internal capital, the Japanese company said. The deal is expected to close in the first half of 2026.

Morgan Stanley is Sompo's financial adviser, while Goldman is advising Aspen on the deal.

(Reporting by Anton Bridge, Kiyoshi Takenaka and Pritam Biswas Editing by Tomasz Janowski, Louise Heavens and Anil D'Silva)