Tokyo's First Dark Sky Park: A Visit to the Beautiful Nature of Kozushima

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Starry sky over Kozushima, designated a Dark Sky Park. Photo: courtesy of Kozushima Tourism Association

Beautiful Tako Beach

From the Miura Bay Observatory, offering a view of Miyakejima and Mikurajima

Kozushima is considered a sacred place for fans of the popular anime Love Live! Superstar!!

Standee panels on display in the Macchare Center

Monoimina-no-mikoto Shrine, dedicated to the founder of Kozushima

Akasaki Promenade, a famous tourist destination

A diving board, popular among beachgoers in the summer

Braised kinmedai dish offered at Yocchare Center's cafeteria

Sundial artwork at Yotane Plaza

View of the village and Maehama Beach from Yotane Plaza

Logo certifying Kozushima as a Dark Sky Park

Water sharing sculpture near the sandy Maehama Beach

Colorful sea dikes of Kozushima Port

Deep-fried ashitaba leaves, a local specialty dish

Information on Kozushima's starry sky on the second floor of the Macchare Center

Photograph of a sky full of stars, taken from the Arima Observation Deck where the Julia Cross stands

Only 4 areas in Japan are designated Dark Sky Places (as of Oct. 2024). Photos 17-18 are courtesy of Kozushima Tourism Association

Many Gifts of Nature on Kozushima

Kozushima can be reached in just under 4 hours on a high-speed jet ferry or around 12 hours on a nighttime large passenger ship, both of which depart from the Takeshiba Passenger Ship Terminal in Tokyo.

Alternatively, it takes around 45 minutes by plane from Chofu Airport. The small island has a circumference of roughly 22 kilometers, an area of 18.58 square kilometers and a population of some 1,700 people. Soon after we arrived, we were taking in the relaxed atmosphere of the island when our tour guide, Eto, greeted us with a smile and said, "My recommendation for lunch would be braised kinmedai (splendid alfonsino)."

He went on to say, "A lot of fish are caught around Kozushima, even compared to other Izu islands, so the fishing industry here is thriving. The highest catch is kinmedai, and they're especially delicious in season between around December and February. You can enjoy kinmedai dishes at the Yocchare Center's cafeteria in the port, or at the inn."

Already looking forward to lunch, we first visited the Tako Bay pier, located on the east side of the island. Mt. Tenjo can be viewed from here, standing as a symbol of Kozushima.

"It's 572 meters tall, which is about the same height as Mt. Takao in Tokyo," Eto explains. "You can take a car up to the sixth station and then walk to the top in about 30 minutes, so it's great even for beginners. Unlike most remote islands, Kozushima has plenty of water and that's thanks to Mt. Tenjo. Rainwater gets filtered through its volcanic rock and earth layers and then springs up across the island."

The Island's Ancient Water Myth

On Kozushima, the village's tap water comes from groundwater. There are many sources of spring water on the island, and one of them is the Tako Spring, located close to Tako Bay.

Eto says, "The Tako Spring is recognized as one of the 57 Famous Springs in Tokyo. The residents of the island often come to draw water from here, so you can frequently enjoy it as coffee or tea. They say the water tastes mellow and delicious."

There is such an abundance of water on Kozushima that a myth called "The Legend of Water Sharing" has been passed down among the island residents.

The story, according to Eto, goes like this: "The gods of the Izu Islands gathered on Kozushima to discuss how to distribute water, the source of life. However, the meeting grew heated and the gods could not come to an agreement. They decided the water should be distributed the following morning on a first-come, first-served basis. The gods of Mikurajima, Niijima, Hachijojima, Miyakejima and Oshima arrived in that order and distributed water for their islands, but the god of Toshima overslept and was late, arriving last. Furious that most of the water was gone, he jumped into what was left and thrashed around. The water splashed all over Kozushima, which is said to be why so many springs exist today."

Darkness Engulfs the Island to Reveal a Sky Full of Stars

The starry sky over Kozushima is so beautiful that stargazing tours are held by local guides. Eto, who works as a stargazing guide as well, told us about the island's night sky.

Kozushima is designated a Dark Sky Park, which is an area certified by an international organization that strives to protect and preserve beautiful night skies untouched by light pollution, which is caused by excessive or unnecessary artificial light. All the residents of Kozushima worked together to get the island certified as a Dark Sky Park, and they succeeded in December 2020.

Eto says, "The Tourism Association began holding stargazing tours in 2017, but they also wanted to pass on the starry sky to the children, so everyone on the island began working on earning a Dark Sky Park certification. To reduce light pollution, they switched the streetlights to those that only shine where light is needed. They also put effort into training local tour guides so that the island residents themselves could expertly explain the stars."

These island-wide efforts were recognized and Kozushima was certified as a Dark Sky Park. Since most of the island residents live close together in one village, light does not get scattered much at night, allowing the stars to shine bright overhead. According to Eto, Yotane Plaza provides great stargazing conditions in particular, and that is where the tours take place.

"Yotane Plaza," he explains, "is an elevated area, so it's undisturbed by the light from the streets and houses. Mt. Tenjo close by also shuts out light from Shikinejima and Miyakejima. That leaves you in deep darkness, which is perfect for stargazing and you can enjoy a grand panorama of the stars spread out above."

On Kozushima, people can see a star called Canopus, which can rarely be seen anywhere on Japan's mainland.

Eto says, "Canopus is the second-brightest star in the entire sky, and it's said that seeing it extends your lifespan. In the past, we've been able to see it on Kozushima in February at around 8 p.m. Since the air is clear in winter, it's the perfect season for stargazing. In addition to Canopus, visitors can also catch the Geminids meteor shower in December, find the Winter Triangle and enjoy a 100% natural view of the starry sky here."

Protecting the Starry Sky Contributes to the Preservation of Nature and Animals

"I feel most excited when I get to talk about the stars," Eto says with bright eyes. 

He believes that protecting the starry sky also ties into preserving the natural environment and wild animals: "Switching the streetlights to those that meet the certification requirements protected the darkness, which allowed nature to return to its original rhythm. In fact, we've seen it have a positive impact on the wild animals. For example, we were able to confirm sea turtles laying eggs on the island for the first time in 10 years."

Whether or not you get to see a sky full of stars depends on luck, but we certainly want to visit Kozushima over and over again to look up at the star-filled sky, knowing that the residents work so hard to protect it and that it contributes to the preservation of the natural environment and wild animals.

Eto Sho

Eto was born in 1992. He was assigned to the Kozushima Tourism Association in 2019 as a local vitalization cooperator, an initiative led by the Ministry of Internal Affairs and Communications in the field of tourism. He became a full-time employee of the Kozushima Tourism Association three years later in 2022. His responsibilities are wide-ranging, such as planning and arranging community-based tours, serving as a guide for various tours and running an online accommodation reservation site called Let's Go to Kozushima.