eSIM or Pocket Wi-Fi? Staying Connected on a Japan Cruise
クルーズ準備シリーズの第3回は、通信の話です。
寄港地を自分の足で歩くなら、地図と翻訳と「船に戻る時刻」の確認のために、データ通信は安全装備のひとつです。しかもこの航路は日本と台湾で国が変わります。eSIMとポケットWi-Fi、どちらを選ぶべきか地元民の目線で整理しました。
この記事は英語が本文です。日本の方にも読んでいただけたらうれしいです。
この記事で分かること
1つのクルーズで変わる3つの通信圏、eSIMとポケットWi-Fiの選び方、無料Wi-Fiの位置づけ、台湾での3つの方法と出発前のオフライン準備が分かります。
急ぐ人は、目次の『Option 1: eSIM — data inside your own phone』から先に読めます。
Local walks in Kyoto & Lake Biwa — beyond the guidebook
When I launched Beyond Kyoto Walks, I promised a cruise preparation series (that first article is here). We have packed for December and sorted out money and IC cards. Third: staying connected.
On my walks, mobile data is not a luxury. It is the map in an unfamiliar port town, the translation of a bus timetable, and the double-check of the all-aboard time. A ship leaves without you — a signal is how you make sure that is not your story.
One cruise, three connectivity zones
On board: the ship's own Wi-Fi. Treat it as an optional paid extra, and check your cruise line's app or website before sailing — packages and prices differ by line and change often, so never budget from someone else's blog post. At sea, I switch to aeroplane mode and enjoy the quiet.
Japanese ports — Naha, Ishigaki, Miyakojima: the full menu — eSIM, rental pocket Wi-Fi, prepaid SIM cards, free Wi-Fi as backup.
The Taiwan day — Keelung: a different country, different SIM rules. A Japan-only data plan covers Japan only — check the coverage list before you buy.
Option 1: eSIM — data inside your own phone
An eSIM is a digital SIM: you install a data plan by scanning a QR code or using an app, with nothing to swap. Install it at home, on your own Wi-Fi, a few days before sailing — not on the pier with one eye on the gangway.
Two checks come before any purchase:
Is your phone unlocked? To use an iPhone with another carrier abroad, it cannot be locked to your home carrier. Apple Support's check: Settings → General → About — "No SIM Restrictions" next to Carrier Lock means unlocked. Anything else, ask your carrier first.
Does your phone support eSIM? Look for an "Add eSIM" option in your SIM settings; no such option usually means no eSIM hardware. On Android, also check whether your plan allows tethering, if you hope to share.
Choose an eSIM if you travel solo or as a couple with modern, unlocked phones: nothing to carry, charge, lose or return, and it works the moment you step ashore. The catch: each traveller needs their own plan — and compatible phone.
Option 2: pocket Wi-Fi — one router for the whole group
A pocket Wi-Fi is a small rented router that connects to the local network and shares it with your phones and tablets. JNTO, Japan's official tourism site, describes Wi-Fi rental as the recommended route for guaranteed access — especially away from the big cities — with rental kiosks at all major airports, or online reservation with hotel delivery.
Choose it for a family or group, for older or locked phones, or when a laptop is coming along: one connection, everyone online. The costs are practical — one more battery to charge nightly, a group that must stay near whoever carries it, and pickup and return to plan into your travel days, not your port days.
The backup layer: free Wi-Fi
Free Wi-Fi is a backup, never the plan. JNTO notes that Japan's major airports offer free terminal Wi-Fi, but warns that free services elsewhere can be patchy and slow. In Taiwan, the government's free iTaiwan network runs more than 5,000 hotspots at transport nodes, tourist spots and public buildings; its official FAQ calls it a basic service at around 8 Mbps — enough for messages and a map check, not big downloads.
The Taiwan day: one day, three ways
For a single day in Keelung, convenience beats thrift:
Simplest: before sailing, install a regional eSIM that covers Taiwan alongside Japan, or a separate small Taiwan eSIM. You step off the ship already connected.
Roaming: one day on your home carrier can be reasonable — check what your carrier actually charges before you sail, not after.
Local SIM: Taiwan's carriers sell tourist prepaid cards, but buying one is a counter transaction. Chunghwa Telecom, for example, asks foreign applicants for a passport plus a second photo ID, in person. Real admin for a few hours ashore — save it for a longer Taiwan stay, and keep iTaiwan as your free backup.
Before you sail: the offline checklist
Download offline maps for Naha, Ishigaki, Keelung and Miyakojima. Google Maps lets you save an area to your phone — but note the limits: offline maps show the streets and your position, yet walking and transit directions are unavailable offline. Use them for orientation, plan the route while connected, and update downloads before they expire.
Screenshot the essentials: the port's name and address in the local language, the all-aboard time, your ship's contact details. Screenshots work with no signal at all.
Set up in advance: install the eSIM profile, confirm the pocket Wi-Fi booking, and download an offline language pack if your translation app offers one.
My short answer
Unlocked modern phones, travelling light: a Japan eSIM, with Taiwan covered by a regional plan or a second eSIM. A group or mixed devices: pocket Wi-Fi, with one keeper of the router. Either way, the offline maps are on your phone before the ship sails. Next in the series: planning your own shore day — a port day on foot, without the ship's tour bus.
Quick checklist: before you sail
□ Unlocked phone first: no SIM restrictions — "No SIM Restrictions" in the carrier-lock settings.
□ Does your phone support eSIM? Look for an "Add eSIM" option in your SIM settings.
□ Download offline maps for Naha, Ishigaki, Keelung and Miyakojima — before you sail.
□ Screenshot the essentials: the port's name and address in the local language, the all-aboard time, your ship's contact details.
□ Set up in advance: install the eSIM profile, confirm the pocket Wi-Fi booking, download an offline language pack.
□ Taiwan day: a regional eSIM that covers Taiwan alongside Japan — a Japan-only plan covers Japan only.
Follow the walks
YouTube: https://www.youtube.com/@BeyondKyotoWalks — walking videos and Shorts, the discovery entrance to this project
Instagram: https://www.instagram.com/beyondkyotowalks/
Thank you for walking with me — stay connected, and be back on board on time.
— Beyond Kyoto Walks
Local walks in Kyoto & Lake Biwa — beyond the guidebook
次に読む
Money and IC Cards in Japan: A Cruise Traveller's Guide
Plan Your Own Shore Day: Walking a Cruise Port Without the Tour Bus
Sources
Japan National Tourism Organization (JNTO), "Wi-Fi in Japan" — free Wi-Fi at major international airports; free Wi-Fi elsewhere can be patchy and slow; pocket Wi-Fi rental kiosks at major airports or online reservation with hotel delivery, recommended for guaranteed access; SIM cards sold at major airports and electronics stores, and your phone must be unlocked to use one: https://www.japan.travel/en/plan/wifi-and-connectivity/
Apple Support, "Use eSIM while traveling internationally with your iPhone" — your iPhone cannot be locked to a carrier to use it with another carrier abroad, and how to check: http://support.apple.com/en-us/HT213448
Apple Support, "How to unlock your iPhone for use with a different carrier" — "No SIM Restrictions" next to Carrier Lock means the iPhone is unlocked: https://support.apple.com/en-us/109316
iTaiwan Wi-Fi (Taiwan government), official FAQ — free service with more than 5,000 hotspots at tourist attractions, transportation nodes, cultural and educational facilities and government offices, at a basic average speed of about 8 Mbps: https://itaiwan.gov.tw/EN/ITaiwanArticle/Contents?articleId=82
Chunghwa Telecom, official prepaid card information — tourist prepaid cards offered in day plans, and foreign applicants apply in person with a passport plus a second photo ID (page in Chinese): https://www.cht.com.tw/home/campaign/prepaidcard/intro
Google Maps Help, "Download areas and navigate offline" — areas can be saved to your device for offline use; walking and transit directions are unavailable offline, and downloaded maps expire and must be updated: https://support.google.com/maps/answer/6291838?hl=en-GB&co=GENIE.Platform=Android
Cover photo: Ukimido (Mangetsu-ji), Lake Biwa, Otsu — Photo: 663highland, CC BY 2.5, via Wikimedia Commons.
— Stay connected —
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Japan eSIM options on Klook
