Mt. Tenjō is the highest mountain on Kōzu island in the Izu island chain south of Tokyo. Even though it’s only 570 meters above sea level, the peak offers alpine scenery, volcanic lakes, and an abundance of wild flowers throughout the year.
Getting to the trailhead: There are two different ferry ports on the island, so your ferry will usually dock at Maehama port (前浜港) unless the waves are high. If that’s the case, then it’ll dock at Takō port (多幸港) on the other side of the island. Be careful when leaving the island as well, because sometimes they change the ferry departure location (but will announce over the town loudspeakers at 8am or you can check the ferry site on-line).
From Maehama port: Exit the ferry and turn left, walking along the pier. On your right is the ferry terminal building. There’s a tourist information center here which has a free hiking map that is well worth picking up. (It’s the same map that you can find in the .pdf file in the map section below). Behind the ferry terminal there’s an open grassy area with a restaurant on your left. Walk through this small park and turn right on the main street. Take an immediate left at the traffic light, following the road as it climbs towards the mountains. Just after turning on the street you’ll see a souvenir shop on your left and another small store a little further up. This is one of the only places to pick up snacks for the hike, though they don’t have a big selection. You’re better off bringing food from Tokyo. Keep climbing on the road, with the river bed on your right. After about 10 minutes you’ll reach a concrete bridge called Tenjinbashi (てんじんばし). You’ll also see a signpost here for the mountain. Turn right here and cross the bridge over the (concrete) river and turn left at the top of the hill. You’ll see a sign that says “1.2km 黒島登山口” (1.2km kuroshima tozanguchi). Follow the narrow road for about 200 meters and then turn left, once again following the signs to “天上山”. You’ll soon pass by an inn on your left called Syuso, which is the closest accommodation to the hike. They have clean rooms, good food, and a great bath on the roof overlooking the ocean. Advance reservations are required, but they’ll pick you up at the ferry terminal and give you a ride to the trailhead as well. Anyway, keep climbing up the road and you will soon reach another road with a brand-new concrete bridge over the river. Veer right here, past the new concrete embankment and continue following the paved road. You will soon find a small cave on your left, signposted as the “bank of chilly wind”. Cold air blows out from this opening, so feel free to crouch down to access the free breeze. Just past this cave, you will reach a junction. Turn left on the road and just after passing by a toilet building on your right you will see the trailhead on your left.
From Takō port: Exit the ferry and walk along the pier to the ferry terminal. You can pick up a paper map of the hike at the information counter. Just behind the ferry building there is a 4-way intersection. Turn right here and walk along the concrete boardwalk to reach a water source (if you need to pick up fresh water for the hike). Otherwise, take the unmarked road that climbs diagonally from the intersection. You can see the kanji 止まれ written on the asphalt indicating for descending cars to stop. Walk up this road and you’ll soon reach a concrete staircase. Turn right here, following the signs to Himukai shrine (日向神社). The road soon terminates at a concrete water storage tank. Climb the stairs to the left of this building and cross the wooden bridge behind the building. The trail climbs up a series of stairs with handrails made out of metal piping. The trail will flatten out soon and you will pass through a stone torii gate and reach the small shrine. Go past the shrine and turn right at the junction, following the signs to 天上山黒島遊歩道. The path enters a really nice forest, so keep walking and turn right at the next junction, which is where the path enters the mountain. The route climbs via a series of switchbacks, with views down to the port. You can see the rocky summit ridge of the volcano above you as well. It should take about 30 minutes to reach a viewpoint, with two metal tubes affixed on either side of the trail. The tube on the mountain side is meant for you to look inside to view a rock formation on the ridge that apparently resembles a buddhist deity. The one on the downhill side is supposedly built so you can hear the sound of the wind. Anyway, after this viewpoint the trail drops down a long gentle slope until reaching a paved road. Walk down the road for about 400 meters and you’ll see the trailhead on your right.
The hike: At the trailhead, there should be plenty of wooden trekking poles here that you can use on your hike. The trail climbs through a row of ferns and you will soon reach the 1st stage point (1合目). There are a total of 10 stagepoints until reaching the summit ridge, and they’re spaced pretty evenly up the slope. The map says to allow 50 minutes to the top of the ridge, but you can easily do it in half that time if you don’t take breaks. The views will open up towards the ocean behind you, so feel free to stop and enjoy the scenery as you climb towards the ridge. Once you do reach the ridge, you’ll be presented with an abundance of hiking options. I recommend taking a right at the second junction you see, with a signpost marked for Sendai ike (千代池). It takes just a few minutes to drop to the shores of the pond, which should be filled with water if it’s been raining recently. If not, then it’s probably nothing more than a puddle. Take a break here on the picnic benches to enjoy the tranquil scenery. From the pond, the trail ducks back into the forest on your left and traverses back up to the main trail. Turn right here and follow the signs towards Omote Sabaku (表砂漠). The path will climb out of the forest and enter a rocky area that looks very alpine in nature. You’ll soon see a trail on your left marked for Kuroshima Tenbo chi (黒島展望地). It’s a 10-minute climb to the top of Mt. Kuroshima, which has incredible views back down to Maihama port. You’ll also get amazing views from the summit itself, so you can skip this side trip if short of time or if the cloud is in. Continue straight on and it’ll take about 15 minutes of gentle climbing to reach Omote Sabaku, the “Front Desert.” The trail is covered with white volcanic sand and it sort of resembles a tiny desert. Ignore the first junction you see (with a trail on your right) as well as the fork on your left (that leads directly to the summit) and you’ll reach the desert area, which is marked by a row of picnic tables. Just past this, you will find a junction on your right marked for Ura Sabaku (裏砂漠), or the “Back Desert”. It is a loop trail that takes about 30 to 40 minutes to complete. Again, if the cloud is in then you can skip this part, as the scenery is the same as the rest of the mountain. If you ignore this trail and continue straight on, you’ll reach a junction that marks the end of the Ura Sabaku loop. To be honest, I skipped this loop trail because I wanted to spend more time around the summit crater, which is the best part of the mountain. Turn left at this junction and follow the signs towards Fudo-ike (不動池). The path climbs quite steeply at first, reaching a lookout point which is apparently one of “Tokyo’s 100 Best New Views.” It looks straight down into a heavily eroded valley and had great views out towards some of Izu’s other islands. After this the trail drops down to the pond, where you’ll find some picnic benches. There’s also a small red hut hidden in the bushes which houses a “bio toilet.” Even if you don’t have to go, it’s worth ducking your head in to see the flushing mechanism via stationary bicycle. Just to the left of the toilets there’s a trail that leads to a stone statue of Fudo Myō-ō. It’s a small statue built into the hillside and worth a visit to check out the moss-covered lantern. From the pond, there are two trails that both form a loop. I recommend going counter-clockwise, so take the path marked for Tenku no oka (天空の丘). The path climbs briefly before reaching a junction. Turn left here for the short hike up to Tenku no oka, which has vistas of Mt. Fuji and the Japan Alps if the air and weather are clear. This trail loops back down to the lake, but retrace your steps back to the junction and turn left. The path climbs for a bit before dropping to a vast meadow. There are three different ponds here (the first one is just down an unmarked trail on your left), and the second pond does not have a path to it. The final pond, called Babaa-ike (ババア池) is another nice puddle of water if there have been recent rains. From here, the trail climbs back up to the crater rim, where it reaches a junction for the trail down to Shiroshima (白島登山口). Ignore this junction for now and head straight on, following the fence posts on your right that have been lined with rope. There’s an old dried crater called Hairanai-ga-sawa lined with white sand. Follow the trail around this and climb past some erosion works on your right and you will soon reach a junction for the summit (最高地点). Turn left for the steep climb to the highest point of the mountain. In clear weather you’ll have panoramic 360-degree views of the Pacific Ocean all around. If the cloud is in then you’ll just have to use your imagination. After enjoying the views. retrace your steps back to the junction and turn right, retracing your steps back to the Shirajima junction. Turn left here, following the concrete path lined with steps. It’s a steep drop but it should only take about 10 minutes to reach the 5th stage point (5合目), which is at the end of a forest road. There’s a toilet here as well as a couple of picnic tables. Just in front of the toilet, you’ll see a trail on your left that ducks into the forest. It’s marked as 下山口 and has a signpost for 村落2.2km. The trail enters a lush forest with lots of shade cover and beautiful trees. Just before the 3rd stage point (3合目), you’ll pass under a stone torii gate and reach a junction for Nachidō (那智堂) temple. Turn right here and walk 5 meters to the temple, which is nothing more than an corrugated metal shack. There are some interesting Buddhist statues inside of the shack though. Retrace your steps and keep climbing down the path. It really starts to steepen here, with plenty of stone steps built in place and a liberal use of climbing ropes lining both sides of the trail. At the 2nd stage point (2合目) you’ll find a water tank. Turn left here and descend through a cedar forest until reaching a paved road. Follow the road down past a few greenhouses (and a junkyard of abandoned vehicles). On your left you can catch vistas of the mountain you just came down. Soon you will reach a new paved road. If you turn left here and cross the bridge, you’ll arrive back at Kuroshima trailhead. Turn right here and continue down the paved road. Take the small road on your left marked for 村落 and it’ll connect with the main road that will lead back to the ferry terminal. All it all, it can take anywhere from 3 to 7 hours for the hike, depending on how many breaks you take.
When to go: This hike can easily be done year-round, but try to avoid the summer heat of July and August, as the lack of shade on the mountain will likely turn you into a dried prune. Also, in rainy/foggy weather it can be a bit of a depressing slog, with no places to escape the elements. June is the peak season for wildflowers, and winter offers your best chance of seeing Mt. Fuji and the Minami Alps.
Access: From Takeshiba ferry terminal (竹芝客船ターミナル) in Tokyo, take a ferry bound for Kōzushima (神津島) and get off at the last stop. During the high season in summer, an advance reservation is highly recommended. The ferry leaves nightly at 10:00pm, arriving on Kōzu island at 10am the following day. The ferry also stops en route on Oshima, Toshima, Niijima, and Shikinejima islands, so you could do some islands hopping on the way if you like. Click here for some English information about the ferry company. There’s also a ferry from Shimoda (下田) port in Izu that takes either 2-1/2 hours or 7 hours, depending on the day of the week.
Live web cam: Click here and select “神津島 前浜南東”
Map: Click here for a full-color map of the island, and here for a detailed map of the summit plateau. You can also pick up paper copies of these maps at the ferry terminal.The map has numbers written in blue from 1 to 29 that correspond with numbered signposts along the trail, so you can cross reference the number on the map with the signposts you see along the way.
Level of difficulty: 2 out of 5 (elevation change 572 meters)
Total round-trip distance: 10km (3 to 7 hours)