JAPANESE Prime Minister Morihiro Hosokawa is spoiled but kind, self-centred but flexible, and always independent. The source for this insight into his personal character is an impeccable one - it is his wife, Kayoko. Since the wife of former prime minister Eisaku Sato told the press in the 1960s that her husband occasionally spanked her, the Japanese media has lived in hope of similar revelations from prime ministerial wives, who are only occasionally a little franker than their Western counterparts. Mrs Sato's disclosure did not, of course, hurt Mr Sato. If anything it bolstered his prestige and he went on to be the country's longest-reigning postwar premier. Mrs Hosokawa was not quite so dramatic, but nevertheless provided some interesting insights in an interview published yesterday in the Mainichi Shimbun. Asked what the Prime Minister was like as husband and father Mrs Hosokawa said: ''He's not the male chauvinist type. The worst I can say about him is he is a bit spoiled and self-centred. It is as if his body has kept growing but he permanently remains asix-year-old.'' Mrs Hosokawa is just as feisty as Hillary Rodham Clinton in defence of her man. Referring to a recent Japanese press report which alleged womanising, she said: ''It was a horrible article. He is kind not only to women but also to men. ''I am not particularly worried although I sometimes tell him to be careful because he can be misunderstood.'' Mainichi queried Mrs Hosokawa on whether her husband was too changeable and she gave a spirited defence: ''That is a good thing. It is natural to change and adapt.'' She said the new Prime Minister was always independent. ''He balances that quality and finds the road he should take,'' she said. ''He is not a person who just sticks to either right-or left-wing dogmas. He's quite flexible.''