The catch is, you need a Japanese PSN account. The demo is known as “Natsubi” and will be available for free. If you remember the Final Fantasy XIII demo cost a bit, so it’s normal to be a bit skeptical, but it is indeed free.
The demo is tweaked a bit compared to the one publicly unveiled at an Odaiba event few weeks back. The demo will be released soon but we don’t have any specific date yet.