He sits stiffly on the willow-green settee, authoritative, imperious, unbending. For Tokugawa Yoshinobu, this day has not brought happiness. Already, in the morning, he, a member of the family descended from the great Shogun the Edo government and whose descendants ruled Japan (or military governor) Tokugawa Ieyasu, who founded in the Imperial name for almost 300 years, he, the guardian of the Tokugawa No robes and masks, has been insulted.

A Japanese correspondent in New York has addressed him in the familiar form, and even in the United States, even in this country, such a thing cannot be bore lightly. He has been forced, for honor's sake, to break off the interview.

Now he is in Washington and there is this Western reporter in fron of him to deal with. His wife, Michiko, is couched near him, looking very elegant, very austere in a long, mist-blue gown.

And, of course, there is a young translator, for, if the truth be known, his wife, who will defer to him during much of the conversation, has a better command of English than he.

Tokugawa Yoshinobu (the last name is equivalent to a Westerner's first name) is not a man to be dealt with lightly even if he is wearing a gray pin-striped suit this afternoon. It's not for nothing that the curators of the National Gallery were close to terror when they heard he was coming to view the showing of Tokugawa No frobes and masks that opens at the Gallery on April 10.

As director of the Tokugawa collection and the Reimeikai Foundation in Japan, he watches over thousands of Textiles and artifacts that have been declared national treasures in his country. Descended from the Tokugawa daimyo (or feudal barons), his status, despite Japan's classless society, is that of a member of a royal family. And he can be unsmilingly forbidding.

Here is a man who agreed to work on a book that would reproduce the Genji picture scroll based on Lady Murasaki's novel of the early 11th century, usually presumed to be the world's first novel, but one which he will quickly inform you is the second, the first being The Hunting of the Bamboo) only if he could have unlimited color proofs - an extraordinary costly way of producing a book. With this man, even though one longs to jump into questions about the relevancy of a daimyo's descendants in Japan today, the cautious route is a better approach.

So Tokugawa is distractedly lanquid when asked about why he has chosen the United States as the first country in which the No robes and masks will be exhibited. Because, he says, Rand Castile of New York's Japan House asked him. He is equally low-keyed when asked about the priceless Genji scrolls, which he owns. He goes into a long discourse, in Japanese, which warrants a few sentences from the translator.

He perks up, though, when asked about his 200 head of cattle. Lo and behold the descendants of the Shogun are in the sense Japanese cowboys. But such cowboys as the Old West would be unfamiliar with. Tokugawa tells you that in Japan, his herd, which grazes on the mountainous forests of the family's remaining land in Northern Japan, are rounded up with a bell.

But the conversation goes back to the Genji scrolls again. It seems that this Tokugawa, out of the family of about 20, is the one with all the family treasures.

Out of the 19 pictures - for the scrolls are really a series of pictures that are overlapped instead of a roll as one would expect from the description - Tokugawa owns 15. The rest? It's difficult to tell in all the back and forth of translation.

During the interview, Tokugawa's wife has spent her time quietly smoking cigarette after cigarette. Does she have an interest in the family antiques, the robes and paintings? She looks momentarily nonplussed. Does she have any particular interest? She starts to answer, only to be interupted by her husband, who says "Yes, sleeping."

For some reason, not clear to a visitor, this answer breaks up the whole party.

"And, of course, she's helpful with my work," he adds, a compliment that Mrs. Tokugawa dismisses with a wave of her hand and a puff o smoke. She relaxes back into the settee.

One wonders, as rumor purports, whether this tranquil Japanese lady, who was raised in Washington and London as the daughter of an ambassador, sleeps with a seppuku knife ready to restore the family honor in blood if necessary as daimyo ladies once did. And so tentatively the subject of daimyo families is brought up again. Tokugawa asks what Americans think "daimyo" means, then goes on to explain that daimyos did not own land in Japan, like a medieval feudal lord, but had the "right and responsibility for the people on the land."

Though they no longer govern the people, Tokugawa, his primary interest other than cattle and the opera (which they say they will see in New York on their return) is in the conservation of the family collection, which dates back to the 17th century.

Many of the family heirlooms have never been seen in Japan, and several years ago when Tokugawa was asked by reporters in Japan why he had never shown the collection in his own country, he replied calmly that he had. What he didn't add, according to a friend, was that he hadn't announced the showing, and therefore, few had seen it.

His collection is the largest private collection in Japan and even the pleas of the Tokyo Museum to exhibit the family art have left him unmoved.

"He doesn't show the robes except every 10 years," says a friend," and, frankly, probably wouldn't show them at all if he thought they would get damaged."

An example of Tokugawa's concern is the fact that he is showing the robes only a few at a time in two-week segments over the six-week period they will be at the National Gallery. This leaves the curators with the arduous task of dismantling the show overnight at the end of the very fortnight.

Tokugawa has made the collection his life's work, along with research on how the Tokugawa family administered its lands during the past. He is a historian and scholar and explains that after World War II, when the descendants of daimyo families had their land taken from htem, many families went into academic scholarship.

Tokugawa, 43, says that his 18-year-old daughter, who is at a university in Tokyo, has an interest in the collection, but that his 15-year-old son is more interested in the family's collection of 1,000 swords and in electronics.

Does the family live in a palace? Do they have several estates? Mrs. Tokugawa starts to laugh again."Oh, no," she says, "we live in a Weatern-style house. We play tennis." It is as if someone suggested that they, as a regal Japanese family, somehow lived in the past. They've never read James Clavell's best-selling novel "Shogun," they say.

That laugh makes one almost confident enough to bring up what one has known all along, that Tokugawa, despite all his hauteur and the fact that he bears the last Shogun's given name, is not really a born Tokugawa. His family is a descendant of a diamyo, and equally as ancient as the Tokugawa clan, but he has been adopted into the family (a common practice in Japan.)

One can see it coming as when he is asked whether the Tokugawa family has hereditary servants attached to it in Japan. He draws himself up on the settee. On the placid face, frown is born; behind the glasses, the eyes glint steely like a saber.

"Family?" he queries the translator. "What does it mean "family?" The translator, who has spent the interview standing, half-bent over in his direction, tries an explanation.

It seems not to please. He answers back, to the translator in Japanese, a lengthy answer that comes out as 'no."

Within seconds the interview is terminated. There are polite bows all around, hands stiffened from the elbow are shaken. The audience is over.