Language Barrier - The web and most of the programming languages which drive it were designed by English speakers or western corporations and hence the majority of documentation and educational resources are also in English. Although much gets translated this still causes a delay in new technologies and trends being adopted.
1. Many of the Japanese coders I've met have put in the effort to learn English. They might not be able to carry fluent geopolitical conversations, but they do tend to have enough chops to read API docs and skim code. Most of the Japanese professionals I've met, in any trade, are ultra professional, and will do whatever it takes to stay on top of their craft, including learning English if needed.
2. It's easy to forget that some of these programming languages, notably Ruby, are actually from Japan. As recently as a few years ago, some of my favorite resources for Ruby were in Japanese, out in front of English.
3. Go to a Japanese bookstore and check out the section for programmers. More recent web languages/tech, like node.js, are not well represented. But then look to the next shelf and you'll see something like Unity stacked to the ceiling. It could be that Japanese coders would rather work on different kinds of projects, spend their time learning new tech in those domains instead of the web, and only see the web as a means to an end. I wouldn't consider this a "language barrier", but rather a difference in priorities.