Last Update: 2015-11-10

Getting a prepaid SIM for travelling to Japan used to be expensive, difficult to purchase, require troublesome activation, or all of the above.  The good news is that things have changed in recent years.


There are two main kinds of cheap Prepaid Unlimited Data SIM for Japan.  The first one, and the focus of this article is 富士卡 7-day.  Its price is HKD95-100 in Ap Liu Street, Sham Shui Po, Hong Kong in October 2015, even though the much higher price RMB298 is printed on the package.

One Size Fits All

The previous incarnation of this Data SIM was limited, but the latest one is unlimited.  It also uses a nice 3-in-1 design that can fit Nano SIM, Micro SIM and large SIM slot.

Data Only

In Japan, it supports data only, i.e. no voice call.  It also has 30MB quota of data for use within mainland China on the first day if you happen to be flying Chinese airline to Japan that requires transit in China.


I used it for 7 days (counted from 00:00 on each calender day in Hong Kong time GMT+8) with my recent trip to Osaka.  It also supports tethering – tested to work well on both LG L22 (rooted) and Nexus 5 KitKat (rooted).  So I inserted it into one of the phones, turned on WiFi Hotspot feature, and shared the connection with the other phone successfully.  This sharing of unlimited data further lowers the cost per person.


It worked fine, with download speeds from 0.7Mbps to 3Mbps at a few locations I tested.  It’s perfect for using Google Maps and Japan railway transit apps, and normal Facebook purposes (although normal is different for everyone – users demanding faster Internet should look at more expensive options).  Even though this SIM card is released by a Chinese company its use is not restricted by the Great Firewall of China, because (if I understand correctly) the data connection roams to Hong Kong via SoftBank.  Therefore Facebook is tested to be working.

Some people say that SoftBank coverage is not as good as Docomo (see the link below).  I have only experienced connection issues in obscure places such as inside a tunnel or basement of a mall, etc.

Known Incompatibilities

In general, smartphones from Chinese companies are especially problematic.  This issue is complicated by the fact that there are different variants of the same phone for different Chinese operators.  (Also see below for Docomo card incompatibilities)

  • The instruction manual states that Meizu models do not work
  • The instruction manual states that BBK (Oppo?) models do not work
  • Specific models and variants of Xiaomi are reported to be incompatible, but some other models may work.


Check whether your phone is incompatible before buying it.

As with many prepaid SIM cards, it has a deadline.

How to Use

[Not verified] If you’re an iOS user, check whether you can manually add or edit an APN.  If not, you may need to download an APN profile for it.  If you are already in Japan and not able to use the Data SIM card due to not being able to enter the APN, thank Apple for screwing you, find a Free WiFi at the airport, then download the APN profile.

  1. Do not use the SIM card before you arrive at Japan
  2. After arriving at Japan, insert the SIM card, turn on the device, turn on mobile data (turn off airplane mode if previously active).  Note that day counting is based on Hong Kong time GMT+8 and starts at 00:00 of the present day, not based on Japan time.
  3. IMPORTANT – Turn on Data Roaming, ignore any warning about incurring huge costs.
  4. IMPORTANT – Add an APN for 3gnet
  5. Test your data connection, if it does not work, make sure the settings are saved, reboot, and try adjusting WCDMA network preferences
  6. (If necessary, set up WiFi Hotspot for sharing with other people)

富士卡 vs Docomo Prepard Data SIM 7-day

[Not verified.  I have not actually tried out a Docomo SIM card.  The following information is what I gathered from my research only.]

The usual kind of cheap Docomo Prepard Data SIM 7-day has high bandwidth LTE for the first 200MB (or 150MB or 100MB) of data usage in each day, with remaining unlimited data being restricted to 200Kbps (or 128kbps) or less.  (Note that there are different variants with even less high bandwidth data quota and/or even lower restricted bandwidth.  There are also more expensive kinds of Docomo Data SIM cards, e.g. 2.2GB data at LTE bandwidth.)


  • Reportedly Docomo has better coverage than SoftBank (in major cities I guess there shouldn’t be too great differences though)
  • Its LTE connection (at least in theory) should be faster than the 3G connection of Softbank (for the first 200MB or 150MB or 100MB each day)
  • Reportedly the 7-day card is actually 8-day because it starts counting from the next 00:00 after the card is activated.
  • From Taobao web site it is priced even cheaper


  • A seller said it’s not compatible with rooted phones – I’m not sure
  • The same seller also said it’s not compatible with dual SIM phones
  • Perhaps caused by phone incompatibilities some people need to force 3G in order for it to work well.  Some people also found that transitioning from LTE to 3G and back may require manual control in their phones.
  • From time to time there are reports from people who bought both cards found that Docomo is unexpectedly slower than 富士卡 at specific locations.  Again (I think) this may be related to a particular phone support of Japan LTE network, or (just a guess) perhaps LTE network in Japan is not yet matured to a point that at every location it has to be faster than 3G
  • There are many variants of Docomo prepaid cards – beware of differences in the high bandwidth quota and the restricted bandwidth

Known incompatibilities

  • It is NOT compatible with Xiaomi and most Chinese brands of smartphones
  • It is NOT compatible with Taiwan brands of smartphones such as some models of HTC
  • It is NOT compatible with Blackberry