Hato Bus Co.'s iconic yellow sightseeing buses are once again becoming familiar sights in Tokyo and Yokohama as they regain popularity among domestic travelers from outside the metropolitan area.

The number of people who took part in tours of central Tokyo offered by the sightseeing bus operator in the 12 months through June soared 9.6 percent from a year earlier to 934,306, a level unseen since the late 1980s, when Japan's economy was experiencing an asset bubble.

Particularly popular are tours that include visits to such sites as the neo-baroque-style State Guest House (Akasaka Palace), which has been open to the public all year round since April last year, and the National Museum of Western Art in the capital's Ueno Park, which was picked in July last year as a World Heritage site.

A Hato Bus official said the Tokyo 2020 Olympics will be the "biggest opportunity" for the Tokyo bus operator, which plans to launch more tours related to the Olympics.

Hato Bus drew a record 1.23 million tourists for its Tokyo sightseeing tours in fiscal 1964, when Tokyo last hosted the Olympics. The figures hovered around 800,000 annually from the mid-1970s before climbing to 944,872 in fiscal 1989. In fiscal 2001, however, the number fell to around 520,000.

Tours designed for foreign visitors comprise 10 percent of its customers, but such demand has been falling. In fiscal 2015, the number of foreign-tourist customers fell 5.6 percent from the year before to 83,879. Those who used tours offered in Chinese tumbled 24.6 percent to 15,267, probably as more Chinese travelers opted to visit other areas in Japan.

Hato Bus saw demand recover from domestic tourists from outside Tokyo as some Tokyo hotels began slashing rates. Tokyo hotels had faced room shortages and surging rates due to a rise in the number of foreign tourists to Japan.