A 23-year-old assistant attache at the Japanese Embassy was killed Sunday night in the District's first traffic fatality of the year after the car he was riding in skidded on a snowy road and crashed into a pickup truck and car, D.C. police said.

Okubo Tatsuo of 4100 Massachusetts Ave. NW, who worked in the accounting section of the embassy, was a passenger in a 1985 Nissan Stanza when the driver apparently lost control about 7 p.m. as she was driving south in the 3100 block of Massachusetts Avenue NW near Observatory Circle.

As the car slid into the northbound lanes, it was struck on the right side by a 1987 Chevrolet pickup truck and a 1977 Plymouth Arrow. The driver, Atsuko Sato, 20, also an assistant attache at the embassy, was taken to George Washington University Hospital where she was in serious but stable condition yesterday.

Sato, of 3900 Tunlaw Rd. NW, was charged with failure to control the vehicle, a noncriminal charge carrying a fine of $100, police said.

Tatsuo, who had worked at the embassy for about a year, was taken to George Washington University Hospital, where he was pronounced dead at 2:19 a.m. yesterday.

The drivers of the Plymouth and the pickup truck were not injured. A passenger in the truck was taken to Georgetown University Hospital where she was treated for minor injuries and released, police said.