Use voice sim card and pocket wifi in Japan?

Hello all,

I'm going to Japan specifically Kansai for a year starting September, and after an afternoon of researching for my best options as far as getting a mobile goes I was wondering if anyone could answer this question for me?

I know most people either go for a pocket wifi/wifi router, or a data sim, or a voice sim when they go, but I really want both internet and calls/SMS.

I have a Samsung Galaxy S3. Is is possible for me to get a voice sim, specifically the one SoftBank offers, and at the same time use a WiFi router? (I was thinking of getting the letinternetjp one). I see on SoftBank that they do incur charges for any 3G data used, but on my phone I have the option to turn off Mobile Data and just use WiFi, so this would not be a problem surely?

Is is possible for me to get a voice sim, specifically the one SoftBank offers, and at the same time use a WiFi router? (I was thinking of getting the letinternetjp one).

Sure it's possible, but it would probably be cheaper and easier to just get a voice+data sim from someone like b-mobile.