There's a lot of people been asking me how do I access internet in Japan? Fyi, the wifi availabality for public use in Tokyo is not as broad as Seoul. In Seoul, you easily find wifi access even if you're just walking on any street like Myeongdong/Hongdae/Gangnam etc, and it's amazing how their public wifi works so well.
I'm quite glad that I made a great choice by booking a guesthouse in Tokyo like how I did last year (different guesthouse). My host in this trip is a super nice guy, I booked 2 rooms for 4 of us from his apartment and he actually provided us 2 pocket wifi so we can access the interenet easily around town. He even loan us the pocket wifi to Osaka and after the trip we gave it back.
Yes, it is better to get a pocket wifi if you're planning to travel in Japan. Of course you don't have to purposely buy a pocket wifi (which I don't think you can buy it here), but you can always rent it before you travel.
This is a site where I find it handy : http://www.beeemobile.com/#!wifi/c3c1
One thing I love about Beee Moblile pocket wifi is their easy pick up and drop off at the airport. All you have to do is make a reservation through their site, make payment and then pick it up when you arrive the airport. The rental charge will be applied from the date of depature until the day you drop it off at the airport. Great thing is there is no deposite charges unlike some other supplier that will actually charge a deposite up to RM600.
You can check the rate here : http://www.beeemobile.com/#!rent--rate/cmvl
A tip for you while using the pocket wifi, remember to bring your charger everywhere as most pocket wifi battery life last up to half day only. As for Beee mobile pocket wifi, their battery usage is up to 12 hours and one pocket wifi can share up to 10 devices!!!
Anyway, I just realize that through Beeee Mobile, you can actually rent digital devices such as the famous casio TR-15, instax mini and also powerbank lololl.. Also, if you are going to travel in the winter season, you can actually rent winter wear from them too! Just rent all in one shot so you don't have to buy it for your trip haahah.
Okay that's it about having internet in Japan! Hope this helps!!