BambooSIM Japan eSIM: Which Unlimited or Fixed-Data Plan Should You Choose?
BambooSIM now sells several Japan eSIM packs that sit directly on KDDI au. Full-speed unlimited, unlimited capped at 10Mbps, and three fixed-data packs for shorter trips.
The line that matters: no daily data allowance on the unlimited options. The phone is not slowed after 1GB, 2GB or 3GB in a day, which is how a lot of travel “unlimited” products actually work.
Prices move. Check the Japan eSIM comparison and the checkout on BambooSIM before you pay. Code ESIMD takes 10% off.
BambooSIM Japan eSIM plans at a glance
BambooSIM splits the KDDI au Japan offer into three families.
| Plan type | Available durations | Mobile data | Hotspot |
|---|---|---|---|
| Full-speed unlimited | 3-31 days | Unlimited at the highest available network speed | Separate: plan days minus 1GB |
| 10Mbps unlimited | 3-10 days | Unlimited at up to 10Mbps | Separate: plan days minus 1GB |
| Fixed data | 4, 7 or 10 days | 12GB, 21GB or 30GB | Shared with the main balance |
On unlimited packs, hotspot equals the number of plan days minus one, in gigabytes. A 31-day eSIM therefore includes 30GB for tethering. A 7-day plan includes 6GB.
Validity on these KDDI packs is Japanese calendar days from first connection in Japan. Activation day is day 1. You must start the eSIM within 180 days of purchase. The packs are data-only: no Japanese phone number.
BambooSIM also sells SoftBank 90-day 30GB / 50GB packs with a different start rule (the clock starts when you claim the QR). This piece compares the KDDI au range above.
BambooSIM
KDDI au 4G/5G
Local Japan IP, no daily cap on unlimited. Read the hotspot line before you tether a laptop.
Best for heavy usage: full-speed unlimited data
The full-speed unlimited pack is BambooSIM’s most complete Japan eSIM.
There is no daily cap, no published fair-use slowdown, and no step-down after a set amount of high-speed data. The eSIM uses the highest speed available from KDDI au.
BambooSIM reports that customers often see 400Mbps to 1Gbps in favourable conditions. That is not a guarantee. Coverage, the handset, congestion and location still decide what you actually get.
This plan is the right default for:
- Remote workers
- Frequent video streaming
- Large photo and video uploads
- Video conferencing
- Content creators
- Travellers using the phone as the primary internet connection
- Stays up to 31 days
Many competing “unlimited” travel eSIMs only give a few gigabytes of high-speed data per day, then throttle hard. BambooSIM’s full-speed pack is built for people who do not want to watch that meter.
Compare
Japan eSIM plans on the live table
Price, local network, 5G and hotspot. Apply ESIMD where the provider accepts it.
Best balance: unlimited data at 10Mbps
Not every trip needs several hundred megabits per second. For a normal holiday, a stable 10Mbps link covers most days:
- Google Maps and other navigation
- WhatsApp and other messaging
- Browsing and bookings
- Music streaming
- Social media
- Standard-quality video
- Translation apps
The 10Mbps plan stays unlimited all day. Speed is capped at 10Mbps from the start. There is no extra slowdown after a daily quota.
It is sold for 3 to 10 days. That is usually the compromise between unlimited use and price.
Tool
How many GB for Japan?
Maps, translation, tickets, stories: size the pack if you are leaning toward 12/21/30GB instead.
Best for controlled usage: 12GB, 21GB or 30GB
The fixed-data packs are for travellers who do not need unlimited.
Three combinations:
- 12GB for 4 days
- 21GB for 7 days
- 30GB for 10 days
All three use full network speed. There is no daily usage limit and no extra throttle after a set amount in one day.
Hotspot is not a separate pot. If a 30GB customer tethers 5GB to a laptop, 25GB remains.
About 3GB per day is enough for many tourists. Heavy streaming, OS updates and cloud backups will chew through it fast. Size it with the data calculator before you pay.
Why direct KDDI au connectivity matters
These eSIMs come through an official partnership with KDDI, one of Japan’s three nationwide operators.
Unlike a roaming eSIM, traffic is not sent out of Japan first. You get a Japanese IP and you attach to local infrastructure.
That can cut the extra hop some travel eSIMs add, and browsing can feel more local (maps, JR apps, convenience-store Wi-Fi logins). Performance still follows KDDI coverage and load.
The eSIM activates on first connect after you arrive in Japan. Buy and install before you fly. Keep the UK line on for bank SMS. Leave EE, Vodafone or Three data roaming off.
Each eSIM is valid for 180 days from purchase, including the plan period. The trip has to fall inside that window.
Hotspot allowances explained
Hotspot matters if you carry a laptop or tablet. Read the hotspot guide before you buy one pack “for everyone”.
On unlimited plans, tethering has its own allowance:
| Plan duration | Included hotspot data |
|---|---|
| 3 days | 2GB |
| 5 days | 4GB |
| 7 days | 6GB |
| 10 days | 9GB |
| 15 days | 14GB |
| 31 days | 30GB |
Data used on the phone stays unlimited. Only data shared with other devices counts against hotspot.
On fixed-data plans, there is no separate hotspot balance. Everything comes from the pack total.
Guide
eSIM hotspot: what the pack actually allows
Tethering caps are where “one plan for the family” usually breaks. Read the line before checkout.
Extra Wi-Fi access for cities, ferries and mountain huts
Every BambooSIM Japan eSIM also includes access to a wider connectivity network on top of mobile data.
Customers can use more than 100,000 Wi2 Wi-Fi points across Japan. Access is also listed on selected ferry routes and at over 100 mountain huts with Starlink.
Useful when KDDI coverage thins out. If a specific ferry or hut is on the itinerary, check that location first: the extra network is only at participating sites.
Free Lawson gift from 24 August to 31 October 2026
Buy an eligible BambooSIM eSIM between Monday 24 August and Saturday 31 October 2026 and you get a voucher for a small complimentary gift at participating Lawson stores in Japan.
Lawson 100, L Minimart and some other stores are excluded. The exact gift, redemption rules and stock sit on the voucher terms.
The promo does not change the eSIM. It is a side benefit if the trip overlaps the campaign.
Our verdict on BambooSIM for Japan
BambooSIM is strongest for travellers who want unlimited data without watching a daily high-speed meter.
- Full-speed unlimited: intensive use and stays up to 31 days.
- 10Mbps unlimited: everyday holiday use at a likely lower price, 3 to 10 days.
- 12 / 21 / 30GB: simple if you already know you will stay light.
Direct KDDI au, a Japanese IP, activation on arrival, and the extra Wi-Fi access are what separate it from a lot of roaming eSIMs. It is still data-only. Check hotspot if a laptop is coming. Confirm the phone in the compatibility tool.
If the handset cannot take eSIM at all, the other Japan article still applies: eSIM vs Pocket WiFi.
Compare
Japan eSIM plans
Ranked from the tracked catalogue. Network, hotspot, checkout price, ESIMD where it applies.
Tool
Does your phone take an eSIM?
iPhone, Galaxy, Pixel: check the model before you buy a QR.
Setup
Activate the eSIM before you board
QR and in-app steps on iOS and Android, on home Wi-Fi.