At first, there was very little information available. The very idea of "illegal" uploads itself I felt was somewhat spurious, as copyright infringement is primarily a civil offense. A bit more information has since become available which has clarified things a little, and from what I can garner, what's going to change come October 1st is approximately zilch. It seems the whole part about punishing "illegal" downloads was added to an otherwise sensible bill at the last minute by the film, music and talent agency cartels for their own benefit and without much thought for the consequences. The following points jump out at me:
- The new law only applies to film and music.
- TV programmes aren't covered as they're broadcast for free anyway. The only exception is if DVDs are on sale. Uploading is probably a different matter mind.
- YouTube and other "streaming" services aren't covered, and for those hosted in the US the DMCA takedown policy takes precedent.
- Copyright infringement remains a civil offense, so the rights holder would have to actually take you to court in Japan to get any kind of fine or sentence. There, they would have to demonstrate that your "illegal" download harmed their business, which any vaguely competent defense could argue down to a slap on the wrist at worst—keep in mind that "illegal" uploads often get to thousands if not millions of people which gives them a case for statutory damages, whereas a single "illegal" download is a single copy which is practically worthless. Likewise, overseas media would have to sue in Japan, which seems an awful lot of trouble for HBO to go to over somebody downloading a single episode of Game of Thrones.
- The most common form of "illegal" downloading is BitTorrent, which uploads what you download as you download it, so anybody using BitTorrent to download "illegal" content can already be pursued for damages anyway.