TOKYO (Reuters) -Japan's SoftBank Group Corp reported an annual net loss of 970 billion yen ($7.18 billion) for the year ended March 31, with the Vision Fund unit posting a quarterly investment loss due to weakness in tech valuations.

That compared with a loss of 1.7 trillion yen in the same period a year earlier.

CEO Masayoshi Son's attempt to bestride the tech investing industry has suffered a series of high-profile reversals after outsized bets through SoftBank's first Vision Fund turned sour and investments made at bubbly valuations via a smaller second fund slumped.

With key architects of that strategy having left, Son has focused on shoring up the balance sheet, cutting his stake in e-commerce giant Alibaba Group Holding Ltd and stepping back from trademark presentations to focus on the listing of chip designer Arm.

Vision Fund assets gaining value during the January-March quarter include e-commerce retailer Coupang Inc and robotics company AutoStore Holdings Ltd, with office-share company WeWork Inc among the fallers.

SoftBank wrote down the value of private portfolio companies in both the first and second funds.

With SoftBank saying it is in defence mode and putting further investing activity on the backburner, speculation has turned to whether the group could buy back more of its shares.

($1 = 135.0500 yen)

(Reporting by Sam Nussey; Editing by Christopher Cushing)