Rokkakudo with Mt Fuji in the background, August 5. (©Sankei by Takashi Hirao)
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The Rokkakudo Hall stands on a small island formed at the tip of a lava flow from an ancient eruption of Mount Fuji. The building, with its hexagonal roof, is a designated cultural property in the town of Fujikawaguchiko. Most of the time, it appears to float on the lake and can only be reached by boat.
In early spring, the water level of Lake Kawaguchi sometimes drops, exposing a land bridge about 150 meters (492 feet) long from Yagizaki Park on the south shore to the hall. This rare phenomenon usually occurs once every few years, but in 2025 it has happened for the second year in a row.
Low Rainfall
Normally, water levels rise in May and June, especially during the rainy season, restoring the view of the hall surrounded by water. In 2025, however, rainfall in June and July was less than 70 percent of average, and the water level has stayed low.
Since the end of the rainy season, brief showers and thunderstorms have occurred, but high temperatures have increased evaporation from the lake's surface. As a result, "since July, the water level has been falling at a rate of about one centimeter (0.4 inches) per day," according to a town official.
By August 1, the water level had dropped 26 centimeters (10.2 inches) compared with July 8, and greenery had spread around the island. Locals now stroll across the exposed lakebed from Yagiki Park to the hall, and tourists are also flocking to the site.
Many take photos of Mount Fuji with the hall in the foreground — a view normally seen only from boats or sightseeing cruises. A couple in their 60s visiting from Chiba Prefecture said, "We saw it featured on TV as a rare sight and decided to stop by."
Concerns for Fish
But the drop in water level has created problems. At the rental boat pier, the reduced water depth has narrowed the mooring area, forcing operators to cut the number of boats available. Town officials are also worried about the impact on fish such as wakasagi (Japanese pond smelt). The shores near Rokkakudo are spawning grounds, and a representative of the Lake Kawaguchi Fisheries Cooperative warned, "The lower water level is shrinking the areas suitable for spawning."
Rising water temperatures could add to the damage. Wakasagi prefer cold water and are said to die when it exceeds 30°C (86°F). "The surface temperature is already up to 27–28°C [80.6–82.4°F]. If it rises further, the fish could weaken and fail to spawn, so we're concerned," the representative said. A late-July survey found little evidence so far of harm to wakasagi, but the combination of drought and extreme heat is fueling concerns.
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Author: Takashi Hirao, The Sankei Shimbun
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