Top bosses from over 20 Japanese companies are holding talks with the Government amid concerns that billions in investment are at risk because of Brexit.
Among those attending a meeting hosted by Prime Minister Theresa May will be the heads of carmakers Nissan, Honda and Toyota, which employ thousands in the UK.
They will be joined by some of Japan's biggest banks - Nomura, Mizuho and Sumitomo Mitsui Banking Corporation - all of which have a significant presence in the City of London.
The meeting comes as the Government faces intense pressure to secure tariff-free access to the EU's single market for car manufacturers following Brexit, as well as secure a trade deal for financial services.
Business and trade ministers Greg Clark and Liam Fox will also be in attendance.
Britain and Japan have established deep rooted trade ties spanning a breadth of business sectors, from the automotive industry and machinery, to pharmaceuticals and retail.
With over 1,000 Japanese businesses in the UK, the country is the UK's 11th largest trading partner, with investment into Britain reaching £46.5 billion in 2016.
The Asian nation has made significant investment in The City of London, with Japanese banks treating the UK capital as a financial gateway to the rest of Europe.
Following the Brexit vote, Tokyo wrote a letter to the British Government urging it to keep free movement of people and remain in the single market and customs union.
It has also called for a transition period for Japanese companies to help shield them from the "unpleasant surprises" that could arise from uncertainty.
The Prime Minister has confirmed that she will extricate Britain from both the single market and customs union.
The Prime Minister's official spokesman said: "We have been clear about the sort of (Brexit) deal we want to secure and that we want trade which is as frictionless as possible.
"I'm sure the PM will be reiterating that when she meets the companies today, and also the commitment to securing an implementation period as soon as possible to give them a period of time to adjust to the new relationship that we are going to build with the EU."
As thousands of British manufacturing jobs hang in the balance, Mrs May has also given unspecified Brexit assurances to Nissan, which has in turn prompted a volley of criticism over whether a so-called "sweetheart deal" had been struck.
While companies are eager for extra detail on what kind of Brexit the Conservatives want, Japanese banks have started to adjust their operations in preparation for the loss of financial passporting rights following the divorce.
Frankfurt has become the financial centre of choice, with Daiwa, Sumitomo Mitsui Financial Group (SMFG), Nomura and Mizuho Securities all bolstering their presence in the Germany city.