
Originally Posted by
webstaa
Yes, you can just get sim-only plans fairly easily. The biggest issue is if you're phone's radios are compatible with the Japanese carriers' bands. Look up what specific model of 5s you have and compare it to the big three's LTE bands. IIRC from the 5s and up they're mostly fine (I haven't checked myself) - the Softbank, AU, and Docomo are still fairly strict about forcing their phones and 2 year contracts on people, but the MVNO (resellers) use their networks.
You can always get a "sim-free" phone and get a similar sim-only plan later on if your 5s doesn't work. There's a fairly wide variety of options now, especially compared with 2012-2013.