Now that you've exhausted downtown, it's time to strike out into the urban wilderness. Obviously there is far more hidden around Koriyama that I could know about or remember, but I'll do my best. There are 4 important streets leading away from the station, and I will follow each of them to the best of my ability.
This is the furthest North of the four streets. It is usually four lanes and has nice wide sidewalks. The Kosumosu bus (written in katakana) runs the full length of it all the way past 49. There is really nothing subtle about this street--what you see is what you get. It is home to a number of non-departmentalized stores, especially clothes, but none of them is hard to find, since they all have large signs outside. There are sports shops, furniture stores, Wal-Mart-esque stores, you name it.
The largest shopping place in this section is home to the Super Zebio sports store. The place is huge, and though I wouldn't normally go there, they do have very good sales periodically. It was also the only place I could find the right bolts for my snowboard bindings, even after going to two specialty snowbaord shops. So yes, they have a lot of stuff. You can also find all your international brand names there, like North Face, Sierra Designs, etc. Also in that same building is an electronics store (with the same crap as everywhere else), a KFC, the only all-you-can-eat restaurant I've ever seen in Japan (it's Italian I think) an overpriced arcade, and tucked away by the KFC is a little pseudo-headshop. This place has odd posters, pipes, jewelry, art books, zippos, and all the camp, kitch, and crapola you could every want to look at. For those of you looking for a taste of home, it also has two kinds of root beer (A&W and Dad's), Jelly-Belly's, and a bunch of other snacks.
Across the catwalk from Zebio is your basic mall with a 100¥ shop, micellaneous clothes, and another arcade. Interestingly, it also has a small community center (next to the arcade) where you can take lessons in a whole host of different subjects. I visited a flamenco class (hot), a ballroom dancing class (hilarious), and a bunch of old ladies cutting up glass to solder them into lamps. There is a whole catalog of classes available from the reception desk.
Continuing West from Super Xebio, there is one other place that might be of interest that is not blatantly obvious by a big colorful sign. It is called Sato Cycles, it is the only cycling proshop I know of in Koriyama. To find it, head West to within about two block of highway 49. Keep looking left down small side streets until you see a tiny shack with one of those antique bicycles with one really big wheel that turns dirctly with the pedals and one very small wheel behind it. The place itself is smaller than my apartment, and it is literally overflowing with stuff. Sato-san, who runs it, is a small, wiry old man who understands a bit of English and is very helpfull. I have made a complete idiot out of myself in that store more than once because I didn't know how to use something I had bought, and he has always helped me out. There is a good chance you won't be able to find what you want amongst the rubble, but ask, because he probably has it. And if he doesn't, he can order it for you. Also, he can get big gaijin-sized bikes for those of us who need them.
Also in that area is a good snowboard shop that occasionally resells boards. Just wander around on the side-streets West of Sato Cycles until you find it. That's what I do.
The street leading right out of the front of the station is Sakura-dori, and it goes west all the way to the rice paddies in the shadow of the mountain ridge between Koriyama and Lake Inawashiro. As with Uneme-dori, most places are pretty self-explainatory with big signs, but I will point out a few of the more interesting spots that make it worth the trek. The fun starts just across Highway 4 with a large musical instrumant shop and a club called Hip Shot on the left. The music store is well-stocked, and the club is supposed to be good, though the one time I tried to go it was closed. On the right side of the street is a downstairs blues bar called Maxwell Street that periodically has live music and an open jam.
Further West you will reach another shopping center aptly named The Mall. That's what it is.
Continuing West, you will eventually come to a Tengu Izakaya and a Kaiten Sushi bar in adjoining buildings. Tengu is like any Tengu, but the sushi place is nice because everything is 100¥. It's a cheap, fast, gently scrolling meal.
A grove of trees on your left is Kaisezan Park. It's a nice enough place, with a track, football/soccer field, baseball park, etc. at the East end. The West end has benches, paths, a pond, some playground equipment, a band shell, and lots of cherry trees for the sakura season. All it lacks is enough empty space for a little pick-up frisbee.
On the West end of the park is highway 49, beyond which there is not much worth talking about. However, between Sakura-dori and Uneme-dori on 49 are a few worthwhile spots. On the left side (headed North) are a well-stocked video rental place and a snappy new onsen. The Onsen has a big hiragana "yu" on the front, and parking in the back. Farther on is a billiards parlor that isn't bad.
Beyond 49 there are three things I will mention. Sakura-dori crosses the route 4 bypass (not to be confused with the regular route 4 that cuts through downtown). If you turn left onto the bypass, eventually you will see on your left another small strip-mall-looking place. In it are two jems: Uniqlo and Wild 1. Uniqlo is a cheap chothing store. Wild 1 is a mecca of camping, fishing, and outdoor gear. It's large, well-stocked, and has reasonable prices (for Japan).
Of all the ways to get from downtown to 49, this is perhaps the best because it often has less traffic. It can take more than 20 minutes on Sakura-dori, and less than ten on this street. To get there, take Sakura-dori from the station to route 4. Turn left on 4 and go about two blocks. As you approach the second pedestrian bridge there is a bizarre kind of double intersection. Under the bridge a turning lane will appear. Take that to the right. One of the first things you will see once you are on Bunka-dori is a 7-eleven on your left with blue-painted pavement in front. After that, the street winds its way out to 49. The only stop worth making that I know of is a tiny (seats about ten, I think) Thai restaurant. After the 7-eleven you will come to a stoplight with lots of blue pavement. The Thai place is on the corner on your left. It is cozy and tastey, but don't go there with more than 4 people or you will wait all night for your food.
Evenutally you will pass Koriyama's water treatment plant, and come to the South side of Kaiseizan park before you reach 49. Across 49 the road turns to brick, and immediately on your left you will find a true buried treasure of Koriyama: Osteria Diva. In my opinion, this is the best restaurant in Koriyama. The chef/patron is Japanese, but I believe he studied and lived in Italy for some time. He makes his own pasta by hand, and he doesn't refrigerate the wine. Also, he has a very large menu for such a small place, and as far as I can tell, everything on it is good. The atmosphere is cozy, friendly, and romantic. If you go there, tell the chef you read this article.
Highway 6 may have a street name, but I don't know what it is, and it's not on any of my maps. Highway 6 is parallel to the furthest South of the 4 streets I am covering. From the South edge of the station it runs West toward Highway 49. There are only two places I know of on this street. About five block from Route 4 on the right side is the Chuo Library. It works like any public library, and has a pretty large CD collection that you can listen to or check out if you have a card. After that, about 2 blocks before highway 49 on the right side is another excellent Italian restaurant called Italian Dining. Try it. You'll like it. Beyond highway 49, highway 6 winds its way out of Koriyama over the mountains and right to the Southern edge of lake Inawashiro. It's probably the quickest way to the lake from Koriyama.