Well, probably because they're promoting like crazy, just look at her Facebook and Youtube. She's been on so many magazines, and she's also doing promotions in China, taking pictures everywhere and what's the most important: the fans are always in contact with her steps.
It's not as if she became popular yesterday... In the 90s she was the most famous singer and fashion leader in Japan, after the divorce and turning to R&B music her popularity decreased.... And it's been steadily increasing again since PLAY
