Kozushima Island: Climbing Mt. Tenjo and Heading to the Sea at Akasaki Promenade

This route takes you across to Kozushima Island, where you will hike Mt. Tenjo rising in the center of the island and enjoy seaside activities in the cove at Akasaki Promenade in the north.

History and Local Charm

Kozushima Island is a gourd-shaped island located about 180 kilometers south of central Tokyo, roughly in the center of the Izu Islands. With a circumference of about 22 kilometers, the entire island is designated as part of Fuji-Hakone-Izu National Park. Rising in the center of the island is Mt. Tenjo, an elegantly shaped trapezoidal mountain at an elevation of 572 meters. Formed by a major eruption in 838 (the 5th year of the Jowa era), the mountain has long been revered as a sacred peak by the islanders. Kozushima Island was once written with characters meaning "island where gods gather." This name comes from the legend that the deity Kotoshironushi-no-Mikoto assembled the gods here to consult on creating the islands of Izu. A legend of water distribution also remains on Mt. Tenjo, where the deities of the Izu Islands are said to have discussed how to share water. Blessed with highly transparent waters and white sandy beaches, it was certified in 2020 as Japan's second International Dark Sky Place. Climb a mountain steeped in myth, step into clear waters, and gaze up at the starry sky at night. It is an island where you can fully appreciate the mountains, the sea, and the sky all together.

Key Highlights

• ​Kozushima Island​​: Maehama Beach, the closest beach from Kozushima Port, stretches approximately 800 meters with sandy shores where you can watch the sunset over the horizon. The "Water Distribution Statue" located at Maehama Beach was inspired by the water distribution legend.
• ​Mt. Tenjo​​: Selected as one of the "100 Famous Mountains of Flowers" and "New 100 Famous Japanese Mountains." At the summit area, you will find Fudo Pond, which forms a heart shape when rainwater accumulates, and the Omote-sabaku Desert, notable for its striking combination of white sand and sheer rock faces. From the New Hundred Views of Tokyo Observation Point, you can look out over the Izu Islands and, if weather permits, even catch sight of distant Mt. Fuji.
• ​Akasaki Promenade​​: A wooden walkway approximately 500 meters long built along the Akasaki coast in the northern part of the island. Featuring a suspension bridge, observation decks, and two diving boards of different heights, it feels like a wooden obstacle course. Corals grow wild in the cove enclosed by the walkway, where many fish such as spangled emperors (hamafuefuki) can be seen.

Recommended Route & Travel Time

The recommended duration is 2 days and 1 night. From Takeshiba Pier, it takes about 3 hours and 45 minutes by high-speed jetfoil, or about 12 hours by large overnight passenger ship. The overnight passenger ship arrives at Kozushima Island in the morning. From Chofu Airport, it takes about 45 minutes by plane. Whether ships arrive at Kozushima Port or Tako Bay is decided on the morning of the day based on waves and wind. Sleeping outdoors is prohibited, so please reserve your accommodation in advance. On Day 1, climb Mt. Tenjo. Leave your luggage at the tourism association inside the Matchare Center or in coin lockers, and pick up the Mt. Tenjo climbing map distributed by the tourism association before departing. It takes about 40 minutes on foot from Kozushima Port to the Kuroshima and Shiroshima trailheads. It is common to ascend via the Kuroshima Trail and descend via the Shiroshima Trail; both trails merge at the Omote-sabaku Desert. From Kuroshima Trailhead to the 10th station at the summit, you will climb 280 meters of elevation in one go, so be careful not to rush. The hike takes about 4 to 6 hours. For safety, descend before sunset. Climbing at night is prohibited. On Day 2, visit Akasaki Promenade. From Kozushima Port, take the village bus bound for Onsen Recreation Center / Akasaki Promenade for 15 minutes, followed by a 1-minute walk from the final stop. Because this is a rocky area where feet cannot touch the bottom, wear a life jacket and avoid swimming alone. Jumping in at low tide carries the risk of hitting the seabed and is dangerous. Swimming is permitted until around 5:00 PM. On the return trip, it is also recommended to stop by the Kozushima Onsen Recreation Center, located along the bus route back to the port.

Experience Summary

Walk across the white desert of Mt. Tenjo, where gods are said to have shared water, discover a heart-shaped pond, and take in views across the Izu Islands. The next day, venture into a clear cove right from a wooden walkway. At night, look up at the sky in this Dark Sky Place. Experience two unique days on Kozushima Island filled with mythology, the sea, and the stars.