Mr Okuyama, now 74, was schooled in England for 10 years as a boy in the 1920s, before returning to a rapidly militarising Japan in the 1930s. But speaking both English and Japanese, and having a foot in both cultures, did not make him immune from the racist politics of the time. The two sides of his upbringing threatened to tear him apart.
He was only three years old when he left Japan by steamer in 1919 for Southampton, by way of Singapore, Colombo, Port Said and Marseilles. His father was one of the founders of Kawasaki Shipping Company, which had benefited from Japan's lack of military involvement in the First World War to amass large stocks of steel. Because London was then the centre of the world's shipping business, old Mr Okuyama was sent to England to oversee the company's affairs there.
The family was quite well- off, living in a three-storey house by Hampstead Heath with a tennis court in the garden. The house still stands, but has been converted into three flats - 'a sign of the times, I suppose,' said Mr Okuyama ruefully.
He went to primary school and then Gaveney Preparatory School on Finchley Road - 'We had a brown uniform with a cap, and I remember freqent visits to the tuck shop.' There was one other foreigner, a Spaniard, in his class, but Mr Okuyama said that neither of them felt the faintest hint of discrimination or racism while at school. 'We didn't feel any different at all. Of course Britain was at the height of its power then. It is a totally different world now.'
It was not until he returned to Japan in 1931 that national differences started to present themselves.
'What struck me was that the Japanese teachers at school were so obsessed with Japan's ranking in the world, in terms of shipping tonnage, or industrial production, and so on. The English were so confident they would never have dreamed of teaching such things.'
He finished school and went on to Tokyo's Keio University, from where he graduated in 1943 with a degree in linguistics. By then Japan was engulfed in full-scale war across East Asia and the Pacific against the US and Allied forces. And Mr Okuyama's 'two-tongued' bilingualism was making him into a Jekyll-and-Hyde figure.
It all crystallised around the family's English maid. 'We had a maid, Isabella Springette. We all called her Bella.' Bella was an orphan, and having been employed by the Okuyama family in their house in London, chose to follow them back to Japan. She was part of the family.
'When I spoke to her, I would say Japan was crazy, that the war was sheer lunacy. But when I was drinking with my student friends and speaking Japanese, I would say 'ra-ra-ra'.' He joined the Navy in 1943, where he received training as a cryptographer. In 1945 he was made a lieutenant at the naval communication headquarters, just in time for Japan's surrender, and the deflation of the nationalist rhetoric that had swept him and his countrymen along.
Bella had been left relatively undisturbed by the authorities during the early stages of the war, even though she was a citizen of a hostile country. She spoke no Japanese, and lived quietly in the family's house, going out with Mr Okuyama's mother to do the shopping and other errands. But when the US bombing began in 1944 she was transferred to a camp for foreign nationals. She returned to the family after the war, but with the food shortages and general level of hardship she went back to England in 1947, after 19 years of service with her Japanese employers.
Throughout the war Bella seemed far more capable of dealing with the contradictions in her situation than the highly educated student of linguistics. One incident, above all else, remains in Mr Okuyama's bilingual memory. 'The day before I went to war she baked me a cake, and said she was proud of me, 'because' she said, 'young men should never stay at home when there is a war'. And I was going off to fight her countrymen. That is so British.'Reuse content