Dear Minh:
NO it is not any corruption. It is just that the default OS settings is in Japanese. When you connect to Internet, it gets activated. So do not fret!! its very simple.
The Disklavier Techie can fix this. It is just to change the language in the con trol setup. But this can only be accessed by the Yamaha Technician.
Please contact your Yamaha Showroom for this.
I too faced this problem and it was resolved by the technician.
Aswath