Recycle shops are to Japan what charity shops are to the UK, and partly out of necessity (ie. recession), partly for environmental reasons (Tokyo was producing so much rubbish in the post-war years there is even an island - Yumé-no-shima / 夢の島 - built on it in Tokyo Bay), these days they're springing up all over the place.
In contrast with a charity shop, however, instead of donating any old junk you think someone else might be willing to buy, you take your any old junk to the recycle shop, and the people who work there decide if someone else might be willing to buy it. The amount of money you get in return is risibly small, but hey, at least you're giving those unwanted possessions a chance to be re-used instead of chucking them straight in the bin. (Also, and in contrast to selling second-hand goods in the UK, you get the same amount regardless of whether it's cash or part-exchange.)
If you're a buyer, on the other hand - and particularly if you are, for example, a cash-strapped ALT just off the bus from Narita Airport - recycle shops can help you furnish your one-room Leo Palace apartment with nearly new and / or barely used bargains.
So with this in mind, here's my guide to the best recycle shops in and around Mito (if you spot any mistakes or can recommend any places I've missed, feel free to leave a comment):
1) Seimiya / せいみや (Tokai)
The original and best recycle shop, as well as furniture and 'white goods' (ie. fridges, washing machines etc), Seimiya has separate departments for hardware, antiques, office and kitchen equipment. For a small fee - and like most if not all of the shops on this list - they are willing to deliver larger items, and for a not-so-small fee, to take away your old kitchen appliances for recycling.
A word of warning: not everything in Seimiya is second-hand, so be sure to check the price and condition before you buy - if the item is new, you may be able to find it cheaper at somewhere like Nitori or Joyful Yamashin.
Directions: Seimiya is on the east side of Route 6 as it goes through Tokai-mura (there's a map on their website).
Stuff Mrs M and I have bought at Seimiya: washing machine, 2 x fridge-freezers, dining table & chairs, vacuum cleaner, zaseki (座席 / those chairs-without-legs often found in Japanese living rooms).
2) Wonder Rex Naka-shi / ワンダーレックス那珂市 (Naka)
The Wonder Rex chain has a new shop in Akatsuka, but the Naka branch is, in my humble opinion, better stocked. I've purchased pretty much every item of clothing I own there, and they also have musical instruments, electrical goods, kitchen goods, toys and sports equipment (although Mrs M tells me the women's and children's clothes tend to be a little on the pricey side).
Directions: The Naka branch is on the south side of a road that runs between Route 349 and Route 6, and part of the San Molino / Homac shopping mall, which is easy to spot because of its large fake windmill (the official Wonder Rex homepage map is here).
Stuff Mrs M and I have bought at Wonder Rex: t-shirts, shorts, trousers, tracksuit tops, presentation set of flower-pattern Cath Kidston coffee mugs
3) Hard Off Mito Minami-inter / ハードオフ水戸南インター (Mito)
Hard Off isn't as big as Wonder Rex, but it sells the same kind of stuff, and if anything is probably slightly cheaper. Don't go there looking for clothes, though, as they really do look like the sort of thing you would find in a run-down branch of the Sue Ryder Shop on Chippenham High Street.
Directions: The Mito branch is near the enormous K's Denki at the Route 50 bypass / Route 6 crossroads. Head towards the expressway from the crossroads and you'll find Hard Off on the right-hand side of the road (the Hard Off homepage map is here).
Stuff Mrs M and I have bought at Hard Off: oven, de-humidifier, chest of drawers, rucksack, baby bath, Bumbo
(Also worth checking out are the Hard Offs at Akatsuka, and on Route 123 at Mashiko, just over the border in Tochigi Prefecture.)
4) Book Off Route 50 bypass / ブックオフ５０号水戸元吉田 (Mito)
Second-hand bookshops are all over the place in Japan, but one of the biggest chains, Book Off, has recently branched out into selling general second-hand goods. The Mito branch specialises in menswear, although they also sell surfboards, wetsuits, golf clubs and so on, along with the usual books, CDs and DVDs.
Directions: It's on the eastbound / north side of the Route 50 bypass, where the bypass meets the road that runs directly from the south exit of Mito Station (the Book Off homepage map is here).
Stuff Mrs M and I have bought at Book Off: t-shirts, polo shirts, trainers, sweaters, and, er, books
(For the more adventurous among you, there is a Book Off recycle superstore - the car park, it says on their website, has more than a thousand spaces - in Maébashi, Gunma Prefecture.)
5) Sohko-seikatsu-kan / 倉庫生活館 (Mito)
There are several recycle shops catering to Ibaraki University students, and the best of them is Sohko-seikatsu-kan. While it is part of a chain, Sohko-seikatsu-kan looks more like the kind of slightly dodgy, independent recycle shops that bargain-hunters like - well, like me - get all worked up about, and stocks furniture, white and electrical goods, along with a smattering of other bits, bobs, odds and ends.
Directions: It's opposite a Max Valu supermarket, on a side road that runs parallel to - and south of - Route 123 (see this map), and not far from Ibaraki University and the Ibaraki Budokan.
Stuff Mrs M and I have bought at Sohko-seikatsu-kan: hand mixer, chest of drawers
6) Seikatsu-kohboh-kan / 生活工芸館 (Mito)
Seikatsu-kohboh-kan may be small but it has a high turnover and, more importantly, is very cheap.
Directions: It's even closer to the University than Sohko-seikatsu-kan, on the T-junction of Routes 118 and 123 (see this map).
Stuff Mrs M and I have bought at Seikatsu-kohboh-kan: fan heater, washing pole
7) Sohgoh Recycle Eco / 総合リサイクル･エコ (Mito)
Sohgoh Recycle Eco is housed in a disused pachinko parlour, and as well as furniture and white goods, they also sell scooters and motorcycles.
Directions: It's on the north side of Route 51 between Mito and Oh-arai (there's a map on their website)
Stuff Mrs M and I have bought at Sohgoh Recycle Eco: gas range
8) Furugi-ya-honpo / 古着屋本舗 (Mito)
Furugi-ya-honpo deals solely in clothing, and while a lot of the second-hand stuff is 'vintage' (ie. expensive), there's a huge amount of stock to choose from, including sale rails outside.
Directions: As per this map, it's on the westbound / south side of the Route 50 bypass, directly opposite Yamada Denki.
Stuff Mrs M and I have bought at Furugi-ya-honpo: hoodie, woolly hat, yukata
9) Kanteidan / 鑑定団 (Akatsuka)
Kanteidan's signage and homepage claim that you can buy and sell 'anything' there, although when Mrs M and went, pretty much the only second-hand stuff we could find was in the extensive clothing section on the top floor.
Directions: Kanteidan is on the eastbound / north side of the Route 50 bypass, between the Mito expressway interchange and the turn off for the old Route 50 at Akatsuka.
Stuff that Mrs M and I have bought at Kanteidan: t-shirts, trainers, manga
9) Yasui-ya / 安い屋 (Mito)
OK, so we're scraping the barrel a bit here, but trust me, Yasui-ya is worth visiting for sheer curiosity value. Most of the goods on display (if you can call it that - it looks more like they were dumped through the front doors off the back of a pick-up truck) have apparently lain untouched for several decades, and while the furniture in particular seems a little over-priced, I get the feeling they would be susceptible to haggling.
Directions: Yasui-ya is just off Route 118, slightly closer to the centre of Mito than Seikatsu-kohboh-kan, and on a side road that leads to the Nijuhsan-yason-keigan temple (二十三夜尊桂岸寺) (see this map).
Stuff that Mrs M and I have bought at Yasui-ya: ceiling lamp
10) Shinei / シンエー
You might not think so if you went there, but Shinei is in fact a slightly more upmarket version of Yasui-ya.
Directions: It's on a back street near Akatsuka Station, as per this map.
There are a few recycle shops in Hitachi-naka, but to be honest they're not much good (the pick of the bunch, Aru-aru, has recently been demolished), although you might want to check out the King Family clothes shop, which is here. A recycle shop in Mito that I have yet to visit is オーディン (Audin? Ohdin? Ordin?), which is on the old Route 50 near Kairakuen (info here).
One final thing: for some reason you won't find many second-hand bicycles in recycle shops. Mountain / road / racing bikes do occasionally turn up, although like the mama-chari / shopping bikes, they tend to be over-priced.