On the little Japanese island of Shikoku, in a little town called Uwajima, is a little but somewhat famous Shinto shrine called Taga Jinja (多賀神社). This means something the lines of "many congratulations", which is a small hint that the place is an ancient fertility shrine. A bigger hint, in the form of a two-meter long wooden phallus complete with intricately carved bulging veins and a sculpted glans, sits in the temple's courtyard.

But the reason most tourists come these days is a drab concrete box of a building that largely dwarfs the wooden shrine next to it. This building is dubbed the Dekoboko Shindô (凸凹神堂), which, if translated fully literally, would mean the Convex-Concave God Hall. In case this is too oblique, the shrine's mon (logo) makes things clearer by placing the kanji for a convex pointy bit 凸 underneath so that it sticks up into the concave hole bit 凹, the end result looking like this:

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Get it? I knew you could! So basically, the hall is a sex museum featuring pornography from all over the world, not much different from the ones in places like Amsterdam and Berlin. Entrance costs a relatively steep ¥800, which really is a bit much given that it's not much bigger than the free operation at the Big Iron Penis Shrine down in Kawasaki.

But there is one excellent reason to trek down to the museum shop: why not buy some ¥300 Yin-Yang Harmony Fortunes (陰陽和合おみくじ) as souvenirs for the folks back home? After all, a normal Japanese temple fortune contains little more than horoscope-style advice, while Yin-Yang Harmony Fortunes will reveal all about the size of your sexual organs and how good you are in bed, also giving you an overall ranking based on those in sumo. Who wouldn't want to be a mighty yokozuna? But alas, we can't all be insatiable stallions, and to illustrate here's an authentic example that might have crushed an ego less gargantuan than mine:

前頭6
男の方:小まら
女の方:ふくれ
取り組:はな息の、出るとき抜いて、くいつかれ。

Maegashira (5th and lowest rank in sumo), number 6 (out of 16)
Male: "Small Penis"
Female: "Bulging"
Match Results: "When the breath comes out the nose, one can eat no more."

That was the literal reading, but of course there's more to it than that: hanaiki means both "nasal breath" and "a person's pleasure" (yes, Japanese euphemisms are weird) and the rest puns on that, so what it really means is something along the lines of "comes once and can't get it up again". Ouch.

But no worries if you can't quite hack Japanese puns, since the fortune also includes a little clay figure graphically illustrating the union described above -- which, for the above case, meant a little toothpick buried in vast folds of flesh. Yipe.

Getting There

First you'll have to get yourself to Uwajima, a non-trivial exercise in itself. It's a couple of hours south of Matsuyama by train or bus, and you'll also pass through if you're doing the Shikoku loop (along the 88 Temple Circuit, mayhaps?) and are coming up from or going to Cape Ashizuri.

But assuming you've landed at the train station, stop by at the nearby tourist office, get yourself a map of town, and ask the staff to point out the shrine because none of the English literature on offer even mentions the place. (There is a semi-discreet Japanese pamphlet, complete with map, available though.) Then head north towards the big landmark of Warei Shrine: once you've crossed the river and reached the steps of the shrine, turn left. The shrine is a few hundred meters ahead, look out for the little signs attached to the lampposts.

References

Personal experience
Lonely Planet Japan, 7th ed.