Overseas investors bought a net 118.54 billion yen in derivative markets and 460.21 billion yen in cash markets, the data showed.
Last week, both the Nikkei and the Topix indexes added over 2%, marking their fifth successive weekly gain.
Both indexes are weaker this week, as a lack of agreement between Washington and Beijing on issues like tariffs' rollback nL2N27O0Q7 and farm purchases nFWN27T0QK, along with missing details nL2N27S0OL on the location and date of signing the 'phase one' deal in US President Donald Trump's speech on Tuesday, raised doubts if the deal will be signed soon.
Japanese investors last week bought 243.2 billion yen worth of overseas equities, their seventh straight week of net purchases, data from the Ministry of Finance showed.