I don't think there are any places to study that are easily accessible. You would really need to speak basic Japanese and have some basic understanding of the subtleties of the culture.
The reasons there are few places to study Japanese crafts in depth are not just a simple matter of economics. There are some cultural attitudes at work as well.
Anything in Japan seems to be commodifiable. With such huge populations crammed into the few flat livable areas of the country it is deeply ingrained in the marketing mind of the Japanese. Textiles classes are no exception. For example, how do you work a long-term indigo workshop where the student truly gets the skills and the teacher isn't wasting their life tied to a vat of indigo?
It takes almost forever to process indigo from seed to dye pot. It takes years to understand the limitations of the indigo dyeing processes. Some of my students have been quick under studies. They are almost always the ones who have mastered some other skill, (often non-related like dancing or cooking.) But for the most part there are a lot of compromises being made. It takes time to learn to make and maintain an indigo vat and time to learn to use it well. It also takes time to figure out how to use it so you aren't going through money as fast as you are indigo.
This may seem discouraging. However, there are foreigners in Japan who have mastered Japanese crafts and arts. We haven't all met face to face but we know each other as we are often in the same books, magazines or TV programs where the writer/director has chosen foreigners love of things Japanese and their dedication to their crafts to show the intrinsic value of these traditional cultural assets.
The non-Japanese faces making pottery, making paper, paper umbrellas, cutting huge frozen tuna with sword-like knives, making flower arrangements, doing the tea ceremony, meticulously repairing antique folding screens, painting in Japanese style, carving wood bloc prints, creating bonsai, lacquerware masters, martial art masters, dancers and someone growing indigo and raising silkworms add some story value to the media.
There is sometimes a bit of a freakshow undercurrent to the plot and it is wise to turn down almost all media requests. Very very few writers and producers and directors of these things take a look at the non-Japanese craftspeople as anything more than 'add value interest' aspect to their project.
Why has someone moved all the way to Japan from Italy, Brazil or India etc. to learn these skills? It is more than just a deep interest in the beauty and sophistication of things Japanese. There is human curiosity and desire to grow that is much more interesting and profound. Is this just harder to get across?
It is easy to get a tad snarky and grumpy in the interview situations you allow yourself to get caught in. It isn't hard to follow the threads of the questions and see where they are leading. The assumptions and presumptions of the interviewer/writer can only be dodged with evasiveness or when cornered by a cold splash of sarcasm quickly followed and wiped up by a tiny Japanese face towel of humbleness.
So all these non-Japanese have found their way to Japan, found masters to study under and continue to work on their crafts. (Many of them before the Internet.) It is not impossible.
I will work on finding out where the opportunities to study Japanese textiles at a level deeper are. Something more than a two hour stencil course or a rubber band shibori experience.
I really appreciate the time taken to email me and ask about opportunities to study here in Japan. If I had more of an entrepreneurial spirit I would establish a small institute dedicated to some areas Japanese textiles I am fond of and value. For the time being I can only take in a few people a year and offer them a room in this creaky house and a little time to share what I can slice off the block (before it gets too old).