But this was absurd. Akiko Tanaka is a successful international banker in her late thirties; she was in a restaurant, herself an 'honourable patron', and she was asking a waiter about the day's menu. Who was she trying to impress? A pimply college student working part-time in a small restaurant to earn enough to take his girlfriend out over the weekend?
After a while the reason began to emerge: Ms Tanaka, although born and raised in Tokyo, is half Chinese, and in a society where even the slightest hint of being different can turn one into an outcast, proving that one belongs takes on supreme importance. Ms Tanaka, perhaps without even realising it, was over-compensating. The waiter probably thought she was mad, but his shift finished at 11 o'clock anyway.
But she has not had it easy in her life, and as she related her family's history, her high-pitched voice became an almost negligible detail. It was a saga that in one sweep took in the tragedy, tumult and new-found prosperity of East Asia in the last half century.
Ms Tanaka's father, Li Neng Tao, was born in Manchuria, north-east China, to a family of landowners. He had a good education, learnt English, and became the local agent of a British textile company that operated out of one of the foreign concessions in Shanghai. But things were starting to look bad in the Thirties, with the rise of the Communists and, at the same time, the advance of the Japanese army into Manchuria.
On 7 December 1941, the day of the attack on Pearl Harbor and the entry of Japan into the world war, Mr Li was arrested by Japanese secret police as a potenial spy for the Allies in Manchuria. He was imprisoned and tortured for eight months - his wife, he discovered later, was killed by a Japanese soldier while he was detained.
At the end of the war, Mr Li married again: this time his wife joined the Communists, and the business-minded ambitious son of a landowner decided to leave her. Eventually he fled to Hong Kong ahead of the 1949 revolution. After a few years struggling to survive in the British colony, he got on a boat to Japan, slipped through the immigration authorities in Yokohama port, and found himself in post-war, US-occupied Tokyo.
Mr Li needed two things: money; and a Japanese wife to legalise his residency in Japan. The first supplied the second. He set up a Chinese restaurant and a laundry service, and then made an irresistible dowry offer to a poor family in exchange for the hand of their 18-year-old daughter.
It was not a love match. He was 37, drank too much, beat his wife often in an anti-Japanese rage when he recalled the war, and never learnt to speak Japanese properly. When Ms Tanaka was born he resented the fact she was not a male heir to his family business, which was starting to prosper. Ms Tanaka remembers frequent fights between her parents when she was young: they became manifestations of her Japanese- Chinese identity struggle.
Her father decided to bring Ms Tanaka up as a Chinese national and a Chinese speaker. As a result, she faced terrible bullying and discrimination all through her schooling, however much she tried to hide her Chinese-ness when outside her home. When she reached 18, she immediately adopted Japanese nationality.
There was one problem no amount of acculturation could overcome: the Family Register, maintained by the state, which lists family trees of permanent residents of Japan. On this Ms Tanaka's Chinese roots are stated, and though it is illegal for others to obtain the register, bootleg copies are available to prospective employers or fathers-in-law who want to check someone's family background. Big companies maintain an unspoken ban on hiring people descended from Chinese, Korean or other ethnic minorities.
Ms Tanaka, who had inherited her father's ambition, decided to travel to Europe to study. She then joined a bank in Paris. She was well paid and her job was going well. But after some years she became dizzy - 'it was an 'unbearable lightness of being', not being rooted anywhere'. And so she applied to come back to the only place she could call home.
Ms Tanaka, back in Tokyo for three years now, misses Parisian life but feels happier in Japan. She visits old Mr Li every week, who lives on his own, having finally separated from Ms Tanaka's mother. Mr Li is set in his ways. But Ms Tanaka is learning to put the past behind her.