30GB, 2GB, or bonus data? Pick roaming before takeoff.

Choose the route by data need and trip length

These are roaming options attached to resident-style Japanese phone lines, not tourist eSIM recommendations. Start with the line you already use for a Japanese number and carrier SMS, then check the exact destination before relying on it.

• ahamo: up to 30GB of the monthly allowance is available without an extra roaming fee in 91 listed countries and regions. No application is required, but the phone must have data roaming enabled.
• Rakuten Mobile: 2GB of high-speed overseas data per month is included in 107 listed areas. After 2GB, speed falls to a maximum 128kbps unless you add 1GB for ¥500.
• povo 2.0 Calls + Data: buy a destination, regular, or wide overseas data topping. The current page lists options from 1GB/3 days in selected regions to larger multi-country packs.
• LINEMO: overseas data is not included in the domestic plan. World Roaming and a paid Overseas Anshin Flat or other applicable route must be active before use.

Use the povo summer bonus only when the second pack has a job

povo's official July 14 announcement says that buying any overseas data topping from 2026-07-14 10:00 through 2026-09-30 23:59 earns a code for the same topping. The code is planned to arrive by email, generally right after purchase, and expires November 10.

• The purchased topping begins automatically when the phone reaches the overseas destination. Start the bonus pack later by entering its code in the povo app after the purchased data ends.
• The offer covers all overseas data toppings, but overseas packs are not available on povo 2.0 Data Only. You need an eligible Calls + Data line with overseas roaming enabled.
• A second identical pack helps a return trip or a longer stay only if its destination, allowance, validity, and November 10 code deadline fit. It is not cash back and does not double the first pack instantly.
• The standard page says customers who joined on or after October 3, 2025 must contact povo support chat to apply for overseas roaming. Finish that identity-checked step before departure.

Know the two limits that change the comparison

ahamo has the largest included allowance here, but it is not an unlimited long-stay solution. Rakuten's smaller allowance is simpler for maps, messages, and an arrival bridge; video, cloud backup, and tethering can exhaust it quickly.

• ahamo counts from the first overseas data-use day in Japan time. From 00:00 Japan time after 15 days have elapsed, overseas speed is limited to a maximum 128kbps until the line connects to data in Japan again; buying more data does not remove that restriction.
• ahamo's overseas ceiling remains 30GB even with the 110GB Oomori option. Going over the available monthly data normally limits speed to a maximum 1Mbps, subject to the separate 15-day rule.
• Rakuten's 2GB overseas use counts toward the tier-setting monthly plan total. Enable overseas roaming in my Rakuten Mobile before departure and connect the line to Rakuten's network in Japan first.
• LINEMO new-number customers cannot join World Roaming until the fifth billing month; MNP and number-transfer routes can be eligible earlier. Its current page also warns that Overseas Packet Flat Rate is scheduled to end on a separately announced date from December 2026 onward.

Protect calls, SMS, and 2FA before turning roaming on

The data comparison does not make overseas voice calls or carrier SMS free. Incoming calls can also cost money, and a dual-SIM phone can place data on the wrong line unless you set it deliberately.

• Check destination support for data, voice, SMS, and the exact phone model. A listed country does not guarantee every imported device or local partner network will work.
• Save the carrier app login, password, email access, support route, and any required code before boarding. Test the line in Japan, update the app, and download offline maps.
• Keep the Japanese line available for bank or account codes, but turn off roaming data on any line that should receive SMS only. Disable automatic mobile-data switching if it could move traffic to a costly home or travel line.
• Use app calling or Wi-Fi for non-urgent calls when appropriate, and check official voice/SMS rates before dialing. Emergency-number availability and calling procedures can differ abroad.

Pick for the next twelve months, not one airport day

A current roaming offer can improve a line that already fits, but it should not drive a resident into the wrong Japanese number, monthly data tier, support route, or identity and payment process.

• Choose ahamo when frequent trips of 15 days or less and a large included allowance matter more than multilingual support. Read the ahamo roaming guide for its detailed limits.
• Choose Rakuten when 2GB is enough for light travel and you already value its tiered domestic plan and Link setup. Review the Rakuten plan guide.
• Choose povo when flexible paid packs and the current second-pack code fit a specific trip; choose LINEMO only after its separate paid roaming route and activation timing are clear.
• Compare the resident plans and FAQ first. This site includes referral links; use the referral page only after checking destination coverage, current roaming terms, identity, payment, and campaign status on the official pages.