China seems to get *slightly* better promotions. Here in Shanghai there are machines where you can print discount coupons for Bic Camera and some other shops before heading off to Japan. Bic Camera's coupon offers a discount of 13% (tax refund+special additional discount). Also, Yodobashi offers that 5% discount for using a UnionPay card on top of the tax-free. But that's also targeting a completely different audience.

And, of course, the NH "weekender fares" from China- extreme discount for only staying the weekend.