Contrary to what people might be thinking, the PlayStation 4 hasn't made a considerable dent in the Japanese market. Sony's home country hasn't received the PS4 well, with sales failing to cross 10,000 units in a single week since the next-gen console's launch two months back in Japan.
There could be multiple reasons behind this. The Japanese gamers aren't too happy that Sony brought their new console to their home market much later than North America. Also, there aren't many Japanese titles (if at all any) available for the PS4. Sales would pick up if a couple of stunning titles come along for the Japanese audience.