The deal will create a joint venture majority-owned by UBS to expand both firms' wealth management offerings, Sumitomo Mitsui Trust said in a statement. It would make UBS the latest foreign asset manager to target Japan's roughly $17 trillion in household assets.
Reuters earlier reported that the deal would be signed by the banks' CEOs in Zurich and expand offerings for both wealthy and ultra-wealthy customers, citing an internal memo from UBS.
"We will establish a joint venture, 51 percent owned by UBS, that will offer a menu of products and services that is more comprehensive than we or SuMi Trust is currently able to deliver on our own," UBS Japan Country Head Zenji Nakamura said in the note.
"This new tie-up will create Japan's first-ever 'one-stop shop' for all the wealth management needs of high net worth and ultra high net worth individuals."
UBS, the world's largest wealth manager, has recently faced stalled earnings in its flagship business managing more than $2.4 trillion for the world's rich as clients stock up on cash and shy away from trading amid geopolitical uncertainty.
Chief Executive Sergio Ermotti earlier on Thursday said the Swiss bank was looking to boost tie-ups with local players outside of Switzerland to support the business' growth.
The deal between UBS and the Japanese trust bank should help both banks boost "wallet share" with existing clients and attract new customers, Nakamura said in the memo, adding a substantial portion of the Japanese lender's 285 trillion yen ($2.63 trillion) of assets under custody hailed from wealthy customers who would be referred to the new company.
UBS clients will get access to the Japanese bank's real estate and trust services, while Sumitomo Trust clients will get access to UBS' wealth management offerings including securities sales and trading, research and advisory capabilities, he said.
Japan, the world's third-largest economy, has long been a target for foreign asset managers, given its relatively high savings rate and number of wealthy individuals. At the end of 2018, personal financial assets totaled 1,830 trillion yen ($17 trillion), according to the Bank of Japan.
The number of wealthy households has been increasing, according to a study by Nomura Research Institute. A record-high 1.3 million households held at least 100 million yen of assets as of 2017.