Closer to the Stars on Kozushima, Tokyo’s ‘Planetarium Island’

Just south of its Izu sister islands Niijima and Shikinejima, Kozushima is a small island with a big reputation. By day, it dazzles with rugged coastlines, mountain trails, and aquamarine beaches. But when night falls, a different kind of natural beauty quietly emerges. As darkness settles and artificial light recedes, the island transforms into a sanctuary for one of the most awe-inspiring sights in nature: a sky blanketed in countless stars.

With wide-open horizons and minimal light pollution, Kozushima becomes a natural planetarium, where constellations glow overhead and the Milky Way can often be seen with the naked eye. In 2020, Kozushima was officially recognized as an International Dark Sky Park (a Dark Sky Island) by the International Dark Sky Association, making it the first in Tokyo and the second of only four locations in Japan to earn the title.

The Road to Becoming Tokyo’s Only Dark Sky Park

Kozushima’s transformation into a certified stargazing sanctuary didn’t happen overnight—it was the result of community collaboration, thoughtful policy, and bold infrastructure improvements. In December 2019, the island adopted a light pollution prevention act outlining the importance of preserving Kozushima’s night skies and setting shared guidelines for the responsible usage of artificial lighting. By mid-2020, more than 400 of the island’s 536 street and road lights were replaced with dark‑sky-friendly warm light fixtures designed to shield upward light and maintain the island’s natural darkness. These upgrades significantly enhanced sky visibility, paving the road towards official recognition.

As a result, in December 2020, Kozushima was officially designated an International Dark Sky Park, becoming the first inhabited municipality in Japan to implement island-wide lighting regulations dedicated to preserving the night sky.

Stargazing in Kozushima: Top Places to See the Stars

While Kozushima’s star-filled sky can be admired from almost anywhere on the island, a few key locations offer a truly exceptional experience. The Akasaki Promenade in the north, the Miura Bay Observatory in the south, and the locally beloved Yotane Square are among the island’s top designated stargazing spots. Each provides unobscured, 365-degree views of the night sky, where even the Milky Way can occasionally be seen and photographed.

Thanks to their distance from the main town, both Akasaki Promenade and Miura Bay Observatory remain free from artificial light. At Yotane Square, visitors can join stargazing tours led by local guides trained in astronomy and local folklore. Using green laser pointers, they trace constellations across the sky, connecting them to both local legends and international mythologies.

Beyond the Stars: Other Ways to Enjoy Kozushima

While stargazing may be Kozushima’s biggest draw among travelers, it’s far from the island’s only appeal. From powdery white-sand beaches and scenic hiking trails to fresh, locally caught seafood and cozy island eateries, Kozushima offers plenty to discover long before the stars begin to shine. Here are a few recommended ways to experience Tokyo’s ‘Planetarium Island’ by day.

See the Island by Bike: Explore Kozushima on Two Wheels

One of the first things you’ll notice upon arriving in Kozushima is its narrow streets and quiet alleyways. While they may seem limiting at first, this is a blessing for travelers who enjoy exploring by bike—or even on foot. With cars often too large for the tightest lanes, bicycles are the ideal way to get around both the main town area and the rest of the island.

Kozushima’s compact size—just 18.58 square kilometers —makes it ideal for cycling. You’re never too far from a scenic lookout point or hidden tropical oasis. Rent a bicycle or scooter from one of the island’s rental shops (Kozushima Auto Service, for example, is right near the port), and begin your journey at Maehama’s beachfront area before heading out to discover the island’s lesser-known areas.

Along the way, you’ll traverse scenic roads and winding coastal paths with striking views, including the picturesque Nagumi Bay trolley remains, its neighboring Buttoshi Rock, and the sacred Monoiminanomikoto Shrine , where daily offerings of fish are made to the island’s deity.

Savor the Island’s Freshest Flavors

Kozushima’s culinary scene shines with creative, local spins on classic and familiar favorites, anchored by freshness and regional ingredients from both land and sea.

In the Maehama area, Hyuga brewery stands out as a stylish bar and restaurant that brews its own craft beer and boasts an impressive menu. Thinks pizzas topped with ashitaba leaves, freshly prepared sashimi, tender duck legs, and fruit-based sorbets and cakes.

Each dish feels like a delicate collaboration between island-grown ingredients and local creativity, making the dining experience here another memorable part of the Kozushima’s experience.

For hearty local meals and convenient access near the port, Ryugu serves up quintessential Japanese fare, while Yocchare Center offers cafeteria-style set meals packed with authentic flavor and generous portions.

If you’re after something casual and satisfying, head to the popular Hawaiian-style food truck `AILANA. Their signature burgers feature juicy beef patties topped with fresh, locally inspired sauces and ingredients. All of `AILANA’s burgers are made to order and can come with very generously sized set options that include access to an all-you-can-drink soda bar.

Take It Higher: Hiking and Trekking Mt. Tenjo’s Trails

Mt. Tenjo, Kozushima’s highest peak at 572 meters above sea level, is the island’s main hiking destination. The mountain’s well-maintained trail begins just on the outskirts of town and winds up through dense forest before breaking into breathtaking panoramic views near the summit.

Recognized as one of the “100 Best New Views of Tokyo,” Mt. Tenjo offers a truly breathtaking vantage point. On clear days, you can glimpse the silhouette of neighboring islands, the Pacific horizon, and the coastline of distant Tokyo. At the summit, lesser-trodden paths branch off along the ridgelines, leading to hidden spots like Fudo Pond, where a heart-shaped island sits in its center. The hike can be steep and winding, so proper footwear, outdoor clothing, and water are essential for comfort and safety along the Mt. Tenjo trails.

Swim in the Island’s Tide Pools: Akasaki Promenade and Beyond

At low tide, the volcanic coastline of Kozushima reveals a hidden underwater world—one best explored in the tide pools around Akasaki Promenade, near the island’s northern tip. Here, local residents and visitors wade into the water and swim among small fish and crustaceans, with natural rock pools creating calm, protected spaces to view marine life up close.

 Akasaki Promenade is also home to one of the island’s most iconic sights: a wooden bridge that connects the scenic boardwalks and diving platforms, where you can dive straight into the turquoise ocean below. It takes about 30 minutes by bicycle to reach Akasaki Promenade from Maehama, but the ride itself, lined with scenic routes, is all part of the adventure.

Plan Your Visit: Access & Safety Tips for Kozushima

Kozushima’s natural richness and quiet charm leave a lasting impact on every traveler. Whether you’re pedaling the island’s coastal roads, hiking its tallest peak, or stargazing under its clear sky, the island invites you to take the time and appreciate all it has to offer. Here, the ocean and the mountains are never far, and each encounter, be it with a local at one of the island’s diners or an attraction, feels intimate.

Due to its remote location and slow-paced island life, a trip to Kozushima requires careful travel planning. Here are a few key tips to keep in mind before you go.

Local transportation

Modes of transport on Kozushima are limited to bicycles and cars, which can both be rented in the island’s Maehama area.

Car and Bicycle Rentals

As vehicle options are limited, advance reservations are highly recommended. For bookings and inquiries, please contact each rental provider directly. Note that most services operate primarily in Japanese.

• Kozushima Auto Service – Bicycle rentals from ¥1,000-¥1,200, motorized scooters from ¥2,300.
• Hamanoya Rental Car – Rental car prices start from ¥12,000 per day.
• Earth Rental Car– Rental car prices start from ¥11,000 per day.

Weather Conditions & Opening Hours

Kozushima’s attractions, activities, and transportation services options are heavily influenced by the season and local conditions. Ferry and flight schedules may be delayed or canceled due to high winds, rough seas, or volcanic activity. Businesses and locations may also close temporarily or operate on reduced hours during off-peak periods, such as Japan’s mid-year rainy season or winter. Please check local weather forecasts and official travel advisories and confirm hours of operation directly with the facility or through the local tourism office before your visit.
Note that most services operate primarily in Japanese.