Can I use my iphone from Australia in Japan?

I am travelling to Japan in November for 2 weeks with my partner. We both are curious of how to access internet/wi fi whilst over there.
We are coming from Australia and I am aware Japan have different frequencies.
My questions are:
1. Can we use our iphones that we purchased in Australia in Japan and
2. If we can use our iphones what are the best options for sim cards for data, internet useage, accessing google maps etc.

Any help would be greatly appreciated!!

1. Can we use our iphones that we purchased in Australia in Japan and

Yes, but it depends on the specific model and whether or not your phones are unlocked.

2. If we can use our iphones what are the best options for sim cards for data, internet useage, accessing google maps etc.

Prepaid sim's are probably best. Check out econnect or bmobile. Alternatively, it may be easier to use a portable wifi hotspot instead.

My daughter is an international flight attendant, and visits Japan very frequently. She uses an iphone purchased in New Zealand and it works perfectly. However, she uses the roaming facility only when she has to, as it is costly. I think she is with Vodafone, which seems to swap to Softbank in Japan. You should download Viber and you can text and call for free nationally and internationally when in a wifi hotspot (i.e.Starbucks) or hotel. You can buy a cheap portable wifi router, but I am not familiar if they work well or not.

Thanks guys :)
I have an iPhone 5s and my partner recently just got a Sony Z2 Xperia. If we buy prepaid sims (bmobile etc) for these phones (assuming they'll be unlocked) is it as easy as going to japan and using them as per usual?

You can get a bmobile data sim from Yodobashi camera. They have locations all over Japan. It costs roughly $30 for the sim and it includes 1GB of data and lasts for 2 weeks, so it should be perfect for what you need. If you do need more data it's as simple as going to their website and paying for more.

Free wifi is not very common in Japan, but 2 places that do offer it are Starbucks and 7-11.

Your phones will definitely work there.

I have an iPhone 5s and my partner recently just got a Sony Z2 Xperia. If we buy prepaid sims (bmobile etc) for these phones (assuming they'll be unlocked) is it as easy as going to japan and using them as per usual?

Prepaid sim cards that include voice service require activation, so that could be problematic. If you need voice then it would probably be easier, but more expensive, to go with a rental sim instead.

Otherwise, I would consider getting a data only sim and using an internet phone service such as skype for your calling.

Thanks! Data sims should be okay as long as we can access the internet I think we'll be good.
In regards to the iPhone - I was looking at b-mobile supported devices. Although the iPhone 5s is supported the model A1453 is not the same model as the iPhones we use in Australia which is A1530. Is this going to cause a problem with the data sim?

It supports the Japanese cellular frequencies. You will have to change the carrier apn, but they'll give you info on how to do that.

One of my friend from Australia rent a sim card and use iPhone 5s in Japan.

This page says several models
https://www.apple.com/iphone-5s/specs/

some of them followed japanese 3g.
some of them followed Japanese 4G(LTE)

Rental Sim
http://rental.cdjapan.co.jp/index_en_jpy_10.html
http://www.pupuru.com/...

Preapaid Sim
http://www.so-net.ne.jp/prepaid/en/

???? I'm confused!, I had a look at the 'Rental Sim Card' page and it says: the card does not support phone calls or ams messages???...how do you make a phoe call and receive?.

If you are only going to be using data, and you two will be together all the time, it might be more cost efficient to rent a portable wifi hotspot. It will allow you to connect at least two devices (and up to 10, depending on which model you rent) and access 4G speeds without the need to switch out the SIM cards in your phones. Also good if you're bringing tablets, laptops, etc that can utilize data. As for making calls, stick to something like Skype and you'll be all good.

???? I'm confused!, I had a look at the 'Rental Sim Card' page and it says: the card does not support phone calls or ams messages???...how do you make a phoe call and receive?.

You would need to use an app for internet based telephone service like skype or line.