Best phone plan to use while in Japan, already have (US) phone?

I already own a Straight Talk operated
iPhone that I planned to bring with me on my month-long trip to Japan. I know that I'm going to rely on it for directions, Google, calling, etc.HOWEVER, Straight Talk s international service plan does NOT include Japan.

That s a problem.

I have done a little bit of research on mobile Wi-Fi hotspot devices, international SIM cards, etc, but would appreciate advice with this dilemma.

You might want to buy a prepaid card in Japan.

Lol