Japan is probably the hardest country in the world to buy iPhone cases, because there's simply too much choice. 

As for the Japanese brands that are popular overseas, I believe Power Support is the most frequently mentioned. Then you have the expensive Gramas cases and their more normal priced Helium line. I currently use a case by AndMesh.

Oh, if you're feeling super rich there's always http://www.squair.me/ 

Yodobashi is tech heaven. I'm a bit of a headphone nut and the last time I went there I just wanted to set up camp at the headphone section, lol.

I hate flip/book style cases as well. The Helium line also has one or two models that are regular leather cases - similar to the Apple cases but with the bottom part also covered. Actually, they have a lot more models out than what their site shows. Go back to the website link I posted and click the link for store locations and find a couple to visit if your plans allow. I'm sure you'll find tons more brands at the listed stores, as well as the rest of Akiba or Shinjuku.

Ah sorry. When you mentioned Yodobashi, I just assumed you meant the ones in Tokyo.

Please take note that most full-size headphones like your ATH-M50x (good headphone, btw) tend to have quite fat plugs (the actual jack is standard 3.5mm, but I'm talking about the plastic/metal enclosure around the jack), so you might want to pay extra attention to the headphone jack opening on the cases you try. I can tell you that my AndMesh case wont fit the M50x stock plug, though it's fine for the Oyaide connectors on my current pair of custom IEMs.

I suppose that's one good point of Spigen and other brands that have "compatible with Beats by Dre" in their marketing/ads. Beats isn't the best headphone in terms of sound, but their plugs are quite big so if a case is advertised as being compatible with them then you can be certain that it'll accept just about any brand of headphone plug.

Glass? have you tried it? you can still use this with some of the casing which is not compatible with full coverage sp.

japan ~~~~ help me buy tempered glass ~~~~  

You can look for lifeproof cases as well. 

Element cases are really more style than protection. IMHO, they're also grossly overpriced. Go for a RhinoShield bumper or Thule Atmos if you really want proper drop protection.

Go here; http://www.mobilereviews-eh.ca

Unfortunately, a case with better drop protection is going to be more bulky than a slim case.  You can't escape that.

They're not bad cases, just not that great when you factor how much they cost compared to the competition. They do look nice, and if you're willing to pay a premium for the looks and metal/carbon material, then its fine. If it's just protection you're after without regard for aesthetic, you can get equal or better with far less exotic materials.

Most of the film/plastic screen protectors don't provide full screen coverage. Even less options if you're looking for a matte/anti-glare or privacy type. It's because of the curved edges on the screen and compatibility with cases (eg; majority of slider cases will not work with 100% coverage protectors). For full coverage protectors, I think you either have to go with tempered glass of some kind (IMOS seems popular on Lowyat) or the messy wet-application type.

Moshi have both film (dry-application)  and glass type protectors. They're called iVisor series.. Just Google search them. The iVisor Glass is not good, according to reviews - touch sensitivity seems to be lacking. The regular non-glass film types are quite good though (also cheaper), and they have both gloss and matte versions. Also washable and re-useable. I had an iVisor AG (anti-glare) and liked it, but in the end I still went back to the Power Support screen protectors, mainly because of the better smudge resistance. I've learned to live with it not covering the edges.