Sompo Japan Insurance Inc., a unit of Japan’s third-largest casualty insurer group by market value, will buy Canopius Group Ltd. of the U.K. for 99.2 billion yen ($963 million) as it expands beyond its aging home market.

Sompo Japan will acquire 100 percent of Canopius by April 30, using its own funds, NKSJ Holdings Inc., the acquirer’s parent company, said in a statement through the Tokyo stock exchange today. Canopius, a participant in Lloyd’s of London, the world’s oldest insurance market, is controlled by funds managed by Bregal Capital LLP, according to a statement distributed by PR Newswire.

The deal is NKSJ’s first foreign acquisition after it paid about 10 billion yen to increase its stake in Brazil’s Maritima Seguros SA in June. Japanese insurers are expanding overseas as an aging society and shrinking population threaten profitability in their home market.

Overseas operations contributed 6.2 percent of NKSJ’s property and casualty net premiums in the last fiscal year, data on the company’s website show. Canopius operates in countries including the U.K., Ireland, the U.S., Singapore and Australia, according to the PR Newswire statement.

Japan’s population of 127 million people had the world’s highest average age in 2010 and will shrink 17 percent by 2055, the fastest decline among developed economies, according to United Nations data.

NKSJ last month more than doubled its profit forecast to 72 billion yen for the year ending March 31, a 65 percent increase from the previous period and the highest total since Sompo Japan and Nipponkoa Insurance Co. combined under the holding company three years ago, data compiled by Bloomberg show.

Canopius’s gross written premiums totaled 692 million pounds ($1.1 billion) in 2012, up from 616 million pounds in the previous year, according to the stock exchange statement.

–Editors: Nathaniel Espino, Andreea Papuc