This is the hike described on pages 223-227 of Lonely Planet's Hiking in Japan 2001 edition.
I decided to do this hike for part of Silver Week 2009 for two reasons; One because Odai ga Hara is apparently still closed due to a landslide and two because this hike is not dampened by koyo (autumn leaves) not yet being in full effect.
What has changed from the book is the bus schedule. We left Imadegawa at 7:04, changed at Kyoto and made it to Omitakashima in time for the 8:59am bus. Horror of horrors, the bus has been moved back to 9:03am. Natsuki and I were the only hikers wandering around in front of the lonely station for about 40 minutes, buying canned coffee, pondering the statue of Gulliver dragging boats and watching two rather old ladies fiddle with their pricey road bikes. The bus showed up around 8:50am and we got on because we had nothing else to do. I asked the driver if it was the bus to Kurodani in Japanese and he gave me a very good explanation of the full route in English. I usually engage in a battle of pride for which language I will speak with people, but he charmed me into throwing in the towel with his complete lack of confidence coupled with his complete competence in communication. As we were sitting in the back of the bus alone, a swishing herd issued from the not yet electronic station. The express train had let out and every mountain walker who was over the hill and ready to roll had turned up in their, subdued, Montbell greens, browns and grays. There were two other foreigners as well and I remarked to Natsuki "We all have the same book."
The bus takes about 30 minutes to get to Kurodani as it goes first to the Gulliver camp grounds, where everyone but us got off. Natsuki began to get skeptical as there wasn't a crowd anymore. The bus then backtracks to an intersection and heads towards Kurodani. One smart loner had gotten off at the intersection and walked to Kurodani, cutting about 15 minutes off of his time. We got off the bus by a small cabin serving pasta and started up into the village. Natsuki's skepticism turned to incredulous as I told her "There's the vending machine where we turn left." Whatever. There is a reason there are no Japanese space pirates. Kurodani is a nice little village that looks like the winters are hard. The road has crystal clear water flowing down both sides. A road leads into the woods were a sign stands saying declaring the hike to be dangerous, for serious hikers with proper equipment who know what they are doing. People die here every year. You might die to so fill out a card. We did and Natsuki was grateful that I talked her into buying boots instead of wearing tennis shoes.
May I take this opportunity, while not doing too much foreshadowing, or overhinting at not so existent excitement, to declare that this IS, indeed, a very hard hike. Not always. And not in some ways that other hikes can be. But this hike has a very, very slim margin of error where you getting all deaded up real quick is entirely possible. This isn't a fun day in the woods that you decide to just go do. Even though it is, without a doubt, fun. And it is in range to just go do. Wear boots. Be in shape. Think about what you are up to and have the confidence to do. Check the weather. Be serious about it.
From the sign the hike is a nice 50 minute stroll in the woods by a stream. The trail can be a little hard to read at times, but there are red marks around to help you. In general, stick to the right side of the river.
The falls start at Gyodome Taki (魚止滝）．Which means, "Where the Fish Stop." And I guess they would. Here we ran into about 8 Japanese people in dry suits and helmets working their way up the river. In the river. I suppose a trail drops down from Gulliver camp grounds as we also ran into the white guy from the bus here. Just below the falls there is a bit off a false crossing. The trail is marked on both sides, so we crossed. But you just cross back again about 50 feet up so you should just stick to the right.
And that's when the CHUDs came after me. From here on it gets real life, batshit crazy. I wish I had pictures but I wasn't sure about the wet factor and the death factor so I left my camera at home. An excuse to go back. My shoes were soaked already though from the false crossing. You start making your way up to the falls by a system of chains nailed into the rock. Some are old and brown, some are new and shiny, but they all seem like a fucking joke. I think I screamed and laughed in terror as I saw each new challenge. In this early area, when you cross back to the left of the river, you have to crawl over a few slippery boulders and trust a log that is lodged in the water. If you make it across that, you have to go on chains and pegs to a narrow ledge and a slippery ladder. It is like playing at being a monkey. A crazy, thrill obsessed water monkey. My kind of monkey.
I could describe each section in detail, but all I could yell at the time was "This is crazy and scary and beautiful!" And that is what it is for the next 1-2 hours. Midway through the falls section you intersect with a trail down from Gulliver. You already think of these people as despicable civilians and you pity and despise them. Keep going because you will be scaling a 75-degree, wet cliff in a few minutes. I also saw a Hibakari (a slim brown snake) on the trail just above this section. The further you climb, the less people you see. The less people you see the more ridiculous Robin Hood fantasy land you enter. The top sections of these falls might be the most beautiful terrain I have seen on earth, but I am prone to capriciousness and overstatement.
Above the falls, the valley narrows and gets stuffy and close. It began to smell like a dump wrapped in an old wet rug, which is to say it smelt like bear. Very possible. We had been passing crushed acorns for a while. We started talking loud and clapping and quickly came over a ridge where everything got hot and dry and sandy. Flies swarmed around us and we had a great view of Biwako (琵琶湖）。
From here on it is what is described in the book; a series of ridge lines run together and you get insane views of the world below. We saw a few other hikers along this stretch, but not many, and we weren't sure where they came from. The flies were the real nuisance through this section. There were at least 30 on me at all times. You drop and climb between the summits and this wore on Natsuki's spirit and my shoes. The last few drops are much steeper and more difficult than the book lets on. Maybe the terrain has changed, or maybe the writer is a descent specialist, either way it got a little rough. A lot of the climb down is through gullies or washes. As I was placing my hands to steady myself a medium sized black snake took notice and gave way a bit. Things got very bear like again and we were joined by brown frogs who were also on their way down. The last two hours went on forever and the sole of my right shoe decided to slip its mortal coil, which made the going quite comfortable. Walking strangely to compensate my pinkie toes began to swell like little pigs in a blanket.
When you finally hit the road at the bottom you feel it is about time. There were "campers" sitting around wooden houses playing with DSs and smoking. I disobeyed most advice I have heard and took of my broken shoes immediately. I walked the last bit to the train station bare foot only to find, of course, that my shoes wouldn't go back on my swollen feet. The train was also swollen with holidy tourists so I got to stand back to Kyoto, try to walk in my shoes to the subway and go shoeless home.
I recommend the hike highly, but it is rough. The last 5 hours are spectacular but nothing to compare to the thrill and beauty of the first 2. I might suggest doing the falls part and taking the cable car back from Hira.
As a side note, I am usually a fairly fast hiker and I finish most hikes an hour or so under the suggested time. Not so here. It took me 7 and a half hours from the trailhead to Kitakomatsu station.