Wifi and phones in Japan

We will be visiting Japan for 2 weeks the end of March. I will be bringing my IPAD. As I need to be available at all times I need to rent a cell phone. I understand I also need to rent a pocket wifi. Now I hear something about a SIM card. I don't even know what that is. If anyone can please help me sort this out I would be most appreciative. I really only need the cell phone to have a number that my family may contact me in case of emergency. Many thanks for any input.

Check out the hundreds of threads that ask this exact same question.

I think you can use b-mobile Visitor Sim 14 days pre-paid or something equivalent.
http://www.bmobile.ne.jp/english/product.html
https://t.iijmio.jp/en/index.html

You can probably purchase at major airports(except Haneda) and/or large electrical stores.

I assume your phone isn't unlocked if you don't know what a sim card is.

You can rent both a phone and wireless module at http://www.globaladvancedcomm.com/
They'll ship the items to your hotel before you arrive or you can pick it up at the airport. This definitely isn't cheap if you need to rent both and I don't think there are many significantly cheaper alternatives.

I would think email / imessage / Line / Skype / Whatsapp would be sufficient for any contact you need. You could look into whether the rental phones can tether internet to your ipad, or if just the wifi module is sufficient. All hotels should provide internet as well, although many of them aren't free.

Thank you for your responses

Do you have a wifi ipad or the 3g/4g version. If its wifi only, then you don't need to worry about sim cards, and could get just a mifi instead.

I really only need the cell phone to have a number that my family may contact me in case of emergency. Many thanks for any input.

In that case you probably don't need a mobile phone. Just use skype, google voice (via the hangouts app), or other voip service to receive calls on your ipad. Or just roam on your home phone, it'll likely be cheaper than renting if you are only going to use it for emergencies.

All hotels should provide internet as well, although many of them aren't free.

Most Japanese hotel chains offer free internet or wifi in the rooms (ryokans/minshuku usually excepted). The western chains tend to charge in the room, but may have free wifi in the lobby.