RUT9XX is using a different LTE module inside that is why it is different. But if you want to just RUTX11 base on what i found on this link: https://www.frequencycheck.com/countries/japan?c_id=2659834
JAPAN BANDS: B1 (2100),B8 (900),B9 (1800),B11 1500 Lower,B18 (800 Lower),B19 (800 Upper),B21 (1500 Upper),B28 (700 APT),B41 (TD 2500)
RUTX11 BANDS: B1 (2100 MHz), B3 (1800 MHz), B5 (850 MHz), B7 (2600 MHz), B8 (900 MHz), B20 (800 MHz), B28 (700 MHz), B32 (1500 MHz), B38 (2600 MHz), B40 (2300 MHz), B41 (2500 MHz)
It is best to actually check with the ISP provider what bands are they using to be sure.
Based on the said bands that RUTX11 is supporting it can work in Japan with the said bands: B1, B8, B28, and B41
I hope it helps