During my last trip trekking around northern Kyushu, I wanted an extra stop between Fukuoka and Nagasaki: I looked at the map, saw Takeo Onsen, and thought: 'Hey, a hot spring town, right on the train line? Sounds good.' Unfortunately, by the time I was looking for accommodation, I found Takeo Onsen to be full - but Ureshino Onsen, a 30 minute bus ride away from Takeo Onsen, still had some open rooms.
I found very little information in English about Ureshino Onsen on the net: I learned it has a small shopping area (typical of most small onsen towns) and that there's a hot spring named after a German scientist who came here to bathe a few centuries back. That was about it. But I'm never one to turn down a chance to stay at a hot spring, so I booked a room for two nights and went.
Ureshino Onsen isn't on the train line, but it is accessible via bus from at least two train stations. If you're coming in (or going to) Fukuoka, your best bet is catching a bus at Takeo Onsen Station, which is accessible via direct trains from Hakata Station. Once at Takeo Onsen, just ask a staff at the train station where the bus stop for Ureshino Onsen is (I managed a halting "Ureshino Onsen no basu...?" before I was pointed in the right direction) and go to wait. It's a local bus, not a highway bus, but when I went it wasn't too crowded and I wasn't the only one carrying luggage.
If you're coming in (or going to) Nagasaki, a closer train station is Sonogi Station. Nagasaki to Sonogi is about an hour, and then a local bus from Sonogi to Ureshino is about half an hour.
Note that as in most small towns, these buses aren't terribly frequent, so it's best to check via Google Maps for routing and timing. On the upside, this also means it's hard to get on the wrong bus, assuming you're at the right stop: chances are there's only one bus at a time at each stop.
There are also direct highway buses connecting Fukuoka and Nagasaki to Ureshino Onsen. Highways buses in Japan are quite comfortable and large, and have a place to store your luggage, which is nice. However, the highway buses are less frequent, and some don't go all the way to the city centre, instead stopping at the outskirts of the town about 2km from the actual city centre. I believe there only three buses a day that run directly from Hakata Station to Ureshino Onsen's main bus terminal (in the city centre), and about four from Nagasaki. As always, Google Maps is your best friend in checking out bus/train options that work for your schedule.
Whether you take a bus or train, it takes about the same amount of time: the highway bus doesn't require a transfer (which might be preferable if you have a lot of luggage) and is cheaper than the train (not by much via Nagasaki, but about 1600 yen less via Fukuoka). Again, though, they don't come super often, and be sure to check that the bus is actually going to drop you off near your accommodation, not some miles away while you're struggling with your bags.
On a side note: the fares on Google Maps are up to date: most English guides to Ureshino Onsen have the older (lower) fares.
So... what's there?
It's a quiet town: if you've ever been to any small hot spring town in Japan, Ureshino Onsen feels similar. The shopping area has lots of places selling local souvenirs (the local specialty is tea, but I also saw some locally grown mixed grains and some handmade goods), but no big malls or department stores. It makes for a pleasant walk around, especially with a foot bath right in the middle of the shopping area: the foot bath is free to use, but it helps if you bring your own hand towel to dry your feet afterwards. One little souvenir shop next to the foot bath also serves snacks, including boiled eggs cooked in hot spring water, black tea soft serve ice cream, sesame dango, and pancakes. I didn't have the pancakes, but I would highly recommend the first three.
Beyond the shopping area are a handful of shrines, parks, a river, and a waterfall, all within walking distance. If you plan out your route, you can probably cover all of them in a day: I did them slowly over two days (because I spent most of my time soaking in the hot springs).
If you have an extra day, you can take a day trip to Takeo Onsen, which is a slightly larger town and has a few more sights to see. Be sure to check bus schedules first, though.
What about food?
And yes, the town has convenient stores: one Lawson, one Family Mart, and one 7/11. So that's another option for food, if you'd like. The Family Mart has a little eating area too.
The local specialty dish is yudofu, or tofu hotpot, but the tofu is cooked in the town's natural hot spring water. The minerals in the hot spring water cause the tofu to "melt" into an almost pudding-like texture. I ate it at my inn for breakfast, and it was served with a salty sesame sauce to be eaten with rice. Very tasty if you like tofu! They even sell plastic bottles of the hot spring water at some stores, if you'd like to try cooking it at home (though I don't know how well that would work for non-Japanese visitors).
Overall, Ureshino Onsen turned out to be a lovely, charming stop that I'm glad to have stumbled on by accident! I think it's also doable as a day trip if you're up early and plan your day well, but I enjoyed staying overnight and relaxing in my inn's baths in between meandering around town.