I was discussing Japanese SIM cards with a friend the other day and noticed that there aren’t really any English resources to help people choose the right SIM card. There is quite a big difference in what you get depending on the provider, so I thought I’d add my 2 cents.

Not all SIMs are equal

If we turn back the clock a couple years - the main carrier SIMs (docomo, softbank, AU) were expensive and predatory. It was easy to get hooked into a 2-year contract costing around 8000 yen a month just for a good data connection. The best you could do was getting something like IIJMO (or a dozen other MVNO options) that would be on the docomo or AU wholesale network, but never be on-par with main-network speed and reliability, often lacking big features like Apple Watch support or 5G.

MVNOs, or “Mobile Virtual Network Operators,” are virtual operators that don’t own their infrastructure or network. These companies, like IIJMO, Mineo, HIS Mobile, have agreements with main network operators (docomo, au, SoftBank, Rakuten) to resell part of their wholesale network, usually at cheaper rates but with varying quality.

But all of that changed when Abe stepped down and Suga took over as prime minister. He made 3 important changes to how the big 3 had to operate:

  • Providers can’t SIM-lock phones - all phones you buy from providers have to have an option to unlock them at any time without paying a huge amount of money
  • Providers can no longer charge a contract cancellation fee to spark stronger competition - so switching from, say, docomo to AU is now free of charge
  • The big providers must offer a cheap plan on their main network that is not MVNOs

This changed the entire market: Carriers can no longer lock customers into contracts for years and need to actually offer something unique, otherwise customers will leave.

The big 3 reacted by first offering cheaper main-network SIMs through their sub-brands (Y!Mobile for Softbank, UQ Mobile for AU). This was already great, because now we had plans that were owned by the big carriers themselves, but the government wasn’t happy about that, and told them again: you have to offer cheaper plans on your main brand!

This gave us 3 new plans: Ahamo from docomo, Povo from AU and LINEMO from SoftBank. The important point here is that all these plans, as I just mentioned, are owned by the big 3, so they are not MVNOs that buy wholesale and piggyback. You get the same speed and network quality as “normal” customers of docomo/au/softbank, with no worse deal. These SIMs will almost always be better than any of the MVNOs available!

So as a first line to choose from, my recommendations would be:

  • On SoftBank: LINEMO, Y!Mobile
  • On NTT Docomo: Ahamo
  • On KDDI/AU: Povo, UQ Mobile
  • On Rakuten Mobile: Rakuten Mobile

For today’s post I will be focusing on Ahamo, Povo (Promo code: LCOD14FW) and Rakuten Mobile.

A quick look at the networks

Ahamo runs on docomo, Povo on AU, and Rakuten Mobile on its own network.

In general, docomo has the strongest network with the fastest speed, followed by AU. Rakuten is the new kid on the block, and while their network is steadily growing, it’s underwhelming for speed and coverage. There are always patches where one is better than the other, but in general, docomo takes the lead. At the time of writing, the AU network has the best coverage on 5G, with docomo lagging slightly behind.

Rakuten Mobile has a unique roaming agreement with AU, so in places where Rakuten Mobile isn’t available yet, it falls back to some offering from AU. This is NOT the same network as main AU or Povo. It is part of the wholesale network that is being rented out to MVNOs. I couldn’t test this as it happens automatically, but I often noticed that my AU line had reception while Rakuten Mobile did not.

Rakuten Mobile often shows ‘5G’ connection, but the speed and throughput is far from it, often comparable with lower 4G speed. Yes, the connection to the tower is 5G, but that doesn’t mean anything if you don’t get 5G benefits; it just eats more battery. This was the only provider where I actually felt that when I entered a URL, I often had to wait a few seconds before anything actually happened, especially in buses or trains.

Bonus points: Docomo/Ahamo allows you to purchase an extra option (currently costing 0 yen/month) that enables 5G SA (5G standalone) that moves you to a dedicated 5G core network, and gives you ridiculous speeds, currently claimed at 受信実効速度は170Mbps~484Mbpsです。

5G SA(Standalone)とはの画像

Only docomo offers 5G SA currently, and the addon is still free for an unspecified amount of time. This is by far the best in terms of speed if that’s what you’re after.

However, while docomo has the best network, it’s also used by a lot of people. So in very crowded areas like at festivals or concerts, it’s usually the worst performing. Ironically, Rakuten is the best for those because it has the smallest customer base.

Data volume and plans

Rakuten Mobile has the most attractive deal here. It’s unlimited, and the price goes up depending on how much data you use, but is capped at 3000 yen for everything beyond 20GB.

毎月のデータ利用量でお支払い金額が決まる 20GB超過後無制限※2で2,980円/月(税込3,278円)さらに使わなければ勝手に安くなる! ※2 公平なサービス提供のため速度制限する場合あり。環境により速度低下する場合あり ※通話料等別費用

Ahamo has 2 options: 20gb for 3000 yen, or 100gb for 5000 yen. If you hit the upper limit you get speed limited to 1Mbps which is still pretty good.


Povo has the most unique offering here: Toppings!

By default, if you pay 0 yen a month, you get 128kbps. That’s very slow, but it’s free and unlimited. Though you won’t be able to do much outside of messaging with it. But did I mention it’s free?

Then you can activate different toppings depending on how much data you need


As with the others, there is a 20GB plan for ~3000 yen, but more interesting options like unlimited for 24h for 330 yen, or 150 GB for 13,000 yen, valid for 6 months.

I’ve been using this SIM a lot on my iPad for its 0 yen option, and then when I have a day of heavy working ahead of me, I buy the unlimited topping and tether to my other devices.

Rakuten Mobile980 yen2980 yen2980 yen2980 yen
Povo990 yen2700 yen4000 yen (50GB) * 2 or 7400 (200GB / 2)330 * days
Ahamo2970 yen2970 yen4950 yen-

Considering this, Rakuten Mobile appears to be the most cost-effective as it never exceeds 2980 yen. However, its network quality is considerably lower. Using a plan like 150 GB for 6 months with Povo can drastically reduce the cost if you don’t use the full 20 GB each month anyway. It’s also a great sub-SIM because of the 0 yen base plan, and you can always add more data when you need it.

Ahamo is the least complicated - either 20 GB or 100 GB. 20 GB was always enough for me, but having the option to upgrade to 100 GB when needed is very nice, and 1 Mbps is still not bad when it runs out.

Roaming when abroad

Roaming is often inconvenient and expensive. It’s usually better to just get a local SIM or eSIM through something like Airalo and be done with it, but with those new plans we may no longer need to do that.

Ahamo surprised when it got announced that it comes with 20 GB of data roaming free of charge!! That’s honestly bonkers and means that in most countries, you can just leave the SIM active and use free data roaming without any additional steps.

This offer is limited to 14 days of constant roaming. If you are longer than 14 days outside of Japan, the speed will get reduced to 128 kbps. You’ll still have unlimited data abroad for messaging, but yeah, it’s gonna be pretty slow. You also can’t purchase additional data when it runs out. You have to return to Japan for it to refresh.

Next in line is Rakuten Mobile - it also gives you 128 kbps unlimited at slow speeds when abroad, or 2 GB at fast speeds free of additional charge (you can toggle fast/slow within the app). Additional volume is available at 1 GB for 500 yen. Still not bad, especially with unlimited at 128 kbps.

Povo is sadly quite bad. They tried to continue with the topping model but all of the options available are pretty pricey - like 5 GB for 14 days for 7080 yen or 3 GB for 7 days for 4280 yen… yeah don’t use this SIM abroad.

Other special perks (Apple Watch, carrier pay, etc)

Ahamo has:

  • Carrier pay (pay through your phone bill)
  • Apple Watch data at 500 yen/month
  • 5G SA (mentioned above)
  • Free 20 GB international data roaming at no extra cost
  • 5 min of each phone call is free
  • Free use of docomo wifi hotspots
  • Synergy if you use d払い

Povo has:

  • No Apple Watch :(
  • Carrier Pay (AUかんたん決済)
  • Unlimited data at 330 yen
  • Unlimited data at 128 kbps at actual 0 yen base plan
  • Free use of AU wifi hotspots, Wi2Premium and a few more
  • Synergy if you use AU Pay

Rakuten Mobile has:

  • Apple Watch data at 500 yen/month
  • Free international data roaming for 2 GB, unlimited at 128 kbps
  • Actual unlimited plan for cheap
  • Carrier Pay…? at some places (Google Play Store), but most don’t support it
  • Ability to activate or re-issue an eSIM within ~2 minutes online
  • Free phone calls, SMS through their apps
  • Gives you extra points on Rakuten Ichiba, synergy with other Rakuten products like Rakuten Card

*Rakuten Mobile offers “free phone calls and free SMS” but it’s the weirdest thing. SMS only works on Android if you use their Rakuten Link app, which for whatever reason doesn’t offer free SMS on iPhone. Free calls is also only if you use the Rakuten Link app, so it’s VOIP and not true cellular - it’s often very janky.

Rakuten Mobile also just stopped working in the past when a new iPhone got released, and some Android phones aren’t even supported for whatever reason (have you ever seen a physical SIM not supported on a phone??), so it’s by far the buggiest of the providers. They also constantly try to upsell your some other Rakuten product, even their Rakuten Link app is plastered with ads…

So David, which one?

In the end it depends on what you want, no? But if you’re still struggling with deciding which one fits the best, my recommendation would be:

  • Ahamo if you just want 20 GB at fast speed, have an Apple Watch and/or travel a lot. The 20 GB roaming is unbeatable, so is 5G SA. 100 GB for 5000 yen is still reasonable for when you need it. The best all-around SIM.
  • Povo for their unique topping mechanism and still very good network, even better than docomo in some areas and crowded places, or with 5G coverage. The 0 yen base plan makes this a no-brainer to have ‘just in case’, or put onto an iPad to always have a 128 kbps data connection on hand. 330 yen for unlimited when needed is damn good for remote working. No Apple Watch option though, and their roaming offering sucks.
  • Rakuten Mobile if you want something unlimited and don’t care much about network, speed, throughput or coverage. It’s good enough in cities and a great secondary SIM to have for when Docomo or AU are overloaded, or when travelling. The ability to quickly move the eSIM to another device has been a life-saver. But, as you can tell from the post, the network is the most ‘meh’, has high latency, lots of dark spots, and other weirdness like their Rakuten Link app having different behavior on iPhone or Android. Also I hate that they constantly try to upsell me when I’m already a customer.

In the end, just try them and see which one you like the most. There is no contract cancellation fee anymore, so it’s very easy to move a number from plan A to plan B and back.

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