At this moment, one of the biggest risk is the SFP of reactor 4.
Japanese government talks they need to evacuate further than 250km (Around Yokohama), but this would be a lie as always.
Dr. Arnie Gundersen warns they need to go further than 450km.
Here FD puts the map just for your information.
From looking at the map, if you are in Tokyo, you seem to need to go down to Nagoya or even more south.
Considering the usage of international airport, Osaka would be a smarter choice.
Have a nice trip.