Many Japanese webstores have a scale that shows the silhouette of the jeans. It usually looks like this.
1 is tight and 5 is a very loose or baggy fit.
This scale is very useful if you know what you're looking for, if you're looking for slim jeans you want the scale to be at 2, maybe 1. You shouldn't trust this scale blindly though, you should also take a look at the measurements, if available. If one store doesn't have measurements, maybe another store on rakuten(or elsewhere) will.
The most useful measurement to determine the fit is, in my opinion, the leg opening, it looks like this in Japanese: 裾 幅(you can also use a
translator). Most cuts are straight or only slightly tapered(look for "66"), so this measurement is usually very useful, if the store gets it right..
You also need to be aware of how high the rise is. 股 上 is Japanese for rise and it will translate to "on crotch." You will probably wear a smaller size in high-rise jeans, I go down 1 or 2 sizes depending on how high the rise is. I'd suggest that you measure the rise on a pair of jeans that you already own and compare that with the measurements, to get some perspective.
If there is no measurement of the rise available you can look at the fly. If it has 5 buttons, it is most likely a high rise and if it has 4 buttons it is probably a low rise. There are exceptions to this, the Pure Blue
XX-004, for example, has 5 buttons in the fly but has a low rise, so you also need to look at the distance between the buttons.
Another way to determine the rise is to see what size the
model at Bears wears, if he wears a size 32 it's probably a low-rise cut, and if he wears size 30, it's probably a high rise. The premise for this method is that the jeans shrink to tagged size.
Actually, I suggest you take more than just that measurement, you should also measure the waist and leg opening. It is important that you measure the waist correctly - measuring the back of the waistband is not the way to do it since the listed waist measurement is the circumference of the waist.
The easiest way to measure the circumference is to lay the jeans flat on the side, line up the both sides of the waistband, measure and double that. Like this:
Go
here for more pictures of how to measure jeans. I suggest you measure the rise all the way up, instead of stopping at the arrow, though. The link shows how
Ironheart jeans are measured, and it is important to keep in mind how they measure the front rise when choosing what size to get in Ironheart's. If you add ~4cm to their supplied measurement you will get the "real" length of the front rise.
Another thing is that the manufacturer's measurements are often more reliable than individual stores' own measurements. Bears's measurements for example aren't very reliable in my experience, I compared my measurements of the SD-103's to those of Bears and I don't think they got anything right at all.
Other manufacturers that take their own measurements are Samurai, Fullcount, Skull Jeans, Studio D'Artisan, well I think most do, so try to find the website of the brand whose jeans you're looking at before buying.
Pretty much all these jeans will shrink to tagged size, size 30 will measure around 76cm after a
warm wash/soak. There are a few exceptions to this rule, Skull Jeans are sometimes larger than tagged size and sanforized jeans, which are rare in this genre, often don't shrink to tagged size.
You should also take stretching into account, both my Samurai's and my SD's have stretched 1.5-2 inches. Size down 2 inches if you like a close fit!
Alright, I think that's everything. Let me know if I forgot something or if anything is unclear!
