Kasagiyama is a relatively low mountain (425m), but the climb certainly gives you a good workout and the view from the top is excellent. The mountain is located between Iizuka City and Miyata Town, about 8km south of Wakamiya Interchange on the Kyushu Expressway. The name Kasagi comes from kasa (umbrella-like straw hat) and gi (put), meaning that the shape of the mountain is like a straw hat put on the ground (as you can imagine, many mountains are called this in Japan!). This picture shows the kind of hat and the kanji for Kasagi.
Sengokukyou camp site is a good starting point
The natural place to start this hike would be the entrance to the trail up the mountain at Sengoku Village, but I think it's better to start further up the valley at the Sengokukyou camp site. It's just below the Rikimaru Dam on Route 471. The camp site is a good starting point because it has plenty of parking, toilets, nice scenery, and also because it means that the first part of the route is a very gentle walk alongside the Yakiyama River, allowing you to stretch your legs before the hard ascent up the mountain.
There are actually two main camp sites in this part of the valley and either of them would be a good place to stay should you want to brave the crowds and the mosquitoes during the summer months (which is the only time it's officially open). I don't know whether you can camp there outside of the summer season, but it might be worth a try. There are also several log cabins available for rent. The phone number displayed on the sign was: 0949-32-0519.
Red footbridge at Sengoku
The first part of the hike follows the Yakiyama River downstream for about 2km. You have to walk along a narrow tree-lined road but there are virtually no cars, so this is very comfortable walking, especially as it's almost flat (slightly downhill of course). The river itself isn't the biggest I've ever seen, but it's pleasant enough with small rapids and several deep pools, two or three of which even have rope swings dangling down from overhanging branches. It looks like an excellent place to stroll and picnic (and swim!!) with the family in the summer. I know that I'll be diving off the swings into those pools at the first opportunity!
After a while you come to Sengokusou, a small hamlet made up of two old hotel/restaurant type places. It's instantly recognisable because there's a big red footbridge across the river (presumably this place was once more popular!). Just after this there's a big bend in the river and then you see the lower campsite, which features a wide open space and concrete steps down to the articially widened river. Continue past this section and you will reach the point where the main road (Rt. 471) crosses the river on a red bridge.
You can follow the main road or (more enjoyably) follow the riverside track in a wide arc
Second camping area and the point at which the main road bridge (red) crosses the Yakiyama River
At this point you have a choice: walk along the main road or follow the river in a big loop. I think it's better to follow the river because that way you can enjoy walking along a traffic-less track instead of dodging cars on the main road. If you choose the same as me, then you'll need to cross over the bridge and take the track immediately to the right. This leads you down the valley following the now concrete-embanked river through fields with a hillside on your lefthand side. At the first small bridge it's best not to cross, but to continue on the left side of the river, walking along the top of the embankment past what looks like an old timber yard (or factory?) until joining another track at a point where the river widens considerably (it's dammed to provide water for irrigation). Eventually you'll come to another small bridge and you should go across this and up into the Sengoku Village, rejoining the main road opposite a house with a very nice garden.
This bridge crosses the river and enters Sengoku Village
The start of the mountain path (in Sengoku Village) is well signposted
Directly opposite the side road from the river, and next to the house with the nice garden, is the start of the track that leads up Kasagiyama. It looks like it is a private road to someone's house, but it has a signpost indicating that it is indeed the entrance to the mountain. Walk up this track, go past the houses, and almost immediately you'll enter the forest on the side of the mountain. The first part of this track is easy enough, but after a couple of hundred meters, the path veers off to the left (all well signposted), and becomes a steep climb through a tangled mass of bamboo. It then continues steeply up through pine and beech forest and is very hard work for 30 or 40 minutes.
...but finally an easy walk along the ridge.
... and then steeply through pine/beech forest...
The path climbs steeply through bamboo forest...
At the top of this steep section, the path suddenly comes out on a ridge and the gradient becomes very gentle, even flat in places. I kept on expecting it to get steep again but it didn't, which was a pleasant surprise.
Small shrine on the ridge
Broad flat summit area of Kasagiyama
In places the ridge widens into open spaces, one of which has a small stone shrine. Then you come to the mountaintop and obviously the site of the old castle, a lower terrace and, at the top of a bank, the surprisingly wide summit itself, some 100m by 30m. It feels more like a park than the top of a mountain!
View towards Nishiyama and Munakata
Shrine at the foot of a tree
The view from the summit is not a 360-degree panorama due to the many trees, but there are several spots around the edge which offer fantastic views across Fukuoka Prefecture. Iizuka City lies to the south-east and looking east you can see Fukuchiyama (900m) sitting above Nogata City. My favorite view was to the north, because it was possible to see all the way to the sea at Munakata near my home. I hadn't expected to be able to see the sea from so far away! However, it was a hazy day so the view was not as clear as I'd have liked. I will have to visit again on a clear day to get better photos.
Coming down from the summit, the first part of the descent is extremely steep and there's a rope to stop you slipping down the hillside. This is only for a short way, however, and the path soon becomes easier and never really gets tough again. It enters a grove of tall straight cedar trees, which is quite a mysterious place. Then, when the cedars run out, the path enters and follows a small stream. Leaving the stream, it follows the contours of the hillside, while the stream falls away steeply down the valley. Suddenly, the path opens up with great views of the valley, the mountain behind and more mountains in the distance. Then it re-enters the forest and descends not too steeply to the car park at Sengokukyou Campsite. The descent seems to be over before you know it!
Only the first part of the descent is steep (and roped)
The path descends gently through a grove of tall cedars
Unfortunately I met some proud deer hunters
Near the end of the walk, the path opens out and offers great views