TOKYO—Japan on Saturday opened its first bullet-train service to the northern island of Hokkaido, part of an extension of high-speed rail to more corners of the country frequented by tourists.

The trains will travel through the Seikan Tunnel, one of the world’s longest, and connect Tokyo with some ski areas in Hokkaido as well as the port city of Hakodate. The new service follows the opening last year of Shinkansen, or bullet-train service, to Kanazawa, a city on the Japan Sea coast known for its feudal castle and gardens.

Japan drew nearly 20 million foreign tourists last year, a record, and visitor numbers in the first two months of this year are showing further gains.

Hokkaido Gov. Harumi Takahashi said she hoped visitors would use the line to view cherry blossoms in the region later this spring. “The prefecture will enter its tourism season soon, so I hope tourists will take the new Shinkansen trains here,” she said.

The new line, however, has drawbacks compared with airlines, including price and time of travel. A trip on the Shinkansen from Tokyo to Shin-Hakodate Hokuto station, currently the final stop, will cost 22,690 yen ($200), which is costlier than some discounted airline tickets. Travel time is slightly more than four hours, while a flight from Tokyo to the area takes only about 90 minutes.

“The bullet trains aren’t a strong option when compared to airplanes as an efficient method of transportation,” said Motoo Kushibiki, an associate professor at Aomori University who specializes in studying the trains. But he said the Shinkansen offers easier access between Hokkaido and the Tohoku region in northeastern Japan and may bring more travelers over the longer term.