Vietnamese Newcomers to Japan: A to Z Guide to Choosing a SIM Card (2026)

Landing at Narita or Kansai airport, the first thing everyone does is turn on their phone — only to realize they have no mobile data. Without a Japanese phone number, you cannot rent an apartment, open a bank account, or even sign up for a supermarket point card. This article is written specifically for Vietnamese newcomers: after reading, you will know exactly which group you belong to, which SIM type to choose, what documents to prepare, and how to avoid overpaying during your first few months.

1. Why prepare a SIM card before flying?

Many technical trainees and international students coming to Japan think "I'll figure it out when I arrive." In reality, your first week in Japan is when you need mobile data the most: contacting your supervising organization or school, using maps to navigate, translating Japanese, and video calling home to report your safe arrival. Meanwhile, free public WiFi in Japan is far less common than in Vietnam — available at coffee shops or train stations, but often requiring tedious registration and suffering from spotty signals.

There are two ways to prepare in advance:

• Order an eSIM before your flight: if your phone is a recent model (iPhone XR or newer, Samsung S20 or newer, and many others), you can order an eSIM online, receive a QR code via email, and scan it to get connected as soon as the plane lands.
• Order a physical SIM delivered to your accommodation: if you already have the address of your dormitory or company housing, you can order in advance to have the SIM waiting for you there.

2. Determine which group you belong to

Choosing a SIM card in Japan depends mainly on your length of stay and the documents you hold. Check which group below applies to you:

Group 1: Tourists, visiting relatives, short business trips (under 90 days)

You do not have a residence card (在留カード / zairyu card), so you cannot sign up for an official postpaid SIM in your name. The right choice is a prepaid eSIM or travel SIM: requires only a passport, works on 5–30 day plans, disposable after expiration, and comes with no contract commitments.

Group 2: International students, technical trainees, engineers (staying 6 months or longer)

You will be issued a residence card right at the airport (if entering via Narita, Haneda, Kansai, or Chubu) or sent one later. With this card, you can register for a monthly SIM card — much cheaper than a travel SIM on a monthly basis. Note: since you won't have a Japanese bank card in your first month, choose a provider that allows payment without a credit card (bank transfer, convenience store payment, or cash on delivery).

Group 3: Settled residents living with family

In addition to individual SIM cards, you should consider fixed home WiFi for the household (a home WiFi router or fiber optic internet). Sharing one internet line for the whole family is always cheaper than each person subscribing to a large data plan.

3. Three SIM card types in Japan — clear understanding in 3 minutes

A common point of confusion for newcomers: Data SIMs do not come with traditional voice calling numbers, but you can still make video and voice calls via Zalo, Messenger, and LINE as normal. If your job does not strictly require a Japanese phone number, a Data SIM is the most economical choice. Conversely, when applying for part-time jobs or signing apartment rental agreements, many places require a real Japanese phone number — in which case you will need a Voice Call SIM.

4. Required documents when registering for a monthly SIM

1. Residence card (在留カード): photo on the front, address registered on the back. If you just arrived and haven't registered your address yet, go to your local city/ward office (区役所/市役所) to register it first — takes about 30 minutes and is free of charge.
2. Delivery address: dormitories, company housing, or rented apartments are all acceptable.
3. Payment method: a Japanese credit card is most convenient, but if you don't have one yet as a newcomer, look for providers accepting convenience store payments, bank transfers, or Cash on Delivery (COD). At HD TELECOM, you can opt to pay after receiving your SIM — no credit card needed.

5. Typical online SIM ordering process

1. Select a suitable data plan (see section 6 below to estimate).
2. Fill in details: full name exactly as on passport, address in Japan, email, and contact info (Zalo/LINE works fine).
3. Upload photos of your residence card (for monthly SIMs) or passport (for travel SIMs).
4. Choose delivery method: eSIM receives a QR code via email within the day; physical SIM ships via post in 1–3 days.
5. Insert SIM, configure APN according to included instructions (usually takes 2–3 steps), restart device, and you're good to go.

6. How much data capacity is enough?

• 3–5GB/month: for messaging, viewing maps, light Facebook browsing; mostly relying on home/school WiFi.
• 10–20GB/month: most popular range for students and trainees — making video calls home a few times a week, watching YouTube at medium resolution.
• 30GB or higher / Unlimited: heavy video streaming, online gaming, or living in accommodation without WiFi.

Pro tip: choose a modest plan for your first month, then track your data usage stats on your device. Most carriers allow you to change plans starting the following month, so don't "buy extra just to be safe" — that is the #1 way newcomers waste money unnecessarily.

7. Five traps newcomers often fall into

1. Signing a 2-year contract at major retail stores for a "free phone": cancellation fees and installment device payments combined can exceed over 100,000 yen. Newcomers unsure of their long-term stay plans should avoid long commitment periods.
2. Buying unofficial "grey market" SIM cards registered under someone else's name: SIMs under another person's name violate regulations, are prone to sudden termination, and prevent you from performing customer service procedures if your device is lost.
3. Not checking if your phone is SIM-locked: phones purchased on installments in Vietnam or second-hand devices are sometimes locked. Check in settings or test with a different carrier SIM before leaving.
4. Forgetting to cancel the old plan when switching carriers: in Japan, automatic payments are standard; forgetting to cancel means continued monthly charges even if unused.
5. Relying on roaming from Vietnamese carriers long term: convenient for the first few days, but per-MB rates are extremely expensive; use it only as an emergency backup.

8. Frequently Asked Questions

Can I order a SIM if I don't have an address in Japan yet?

Yes, in two ways: choose an eSIM (received via email, no address needed) or order in advance and have it delivered to the hotel/dormitory you will be arriving at.

How long does it take to get connected?

eSIM: connected on the day of order, often within minutes. Physical SIM: add 1–3 days for postal delivery.

Will phones brought from Vietnam work?

Most unlocked phones supporting Japanese network bands will work fine (models from 2018 onwards are almost always compatible). If your phone is too old, consider buying a phone in Japan — second-hand phone prices in Japan are quite affordable.

What if I want to keep my Vietnamese number to receive bank OTPs?

Before flying, register for a number reservation service with your Vietnamese network provider (a few thousand VND/month), insert the Vietnamese SIM in slot 2 or leave it in an old phone at home. Once in Japan, use your Japanese SIM as the primary connection and use the Vietnamese SIM only to receive SMS messages when needed.

Conclusion

Selecting a SIM card in Japan is not complicated as long as you follow the proper steps: determine stay duration → choose SIM type → prepare documents → select appropriate data allowance. If you are still unsure which plan suits you best, HD TELECOM's Vietnamese team provides free consultation in Vietnamese — simply message us via our contact page with information about which group you belong to in section 2, and we will recommend the most cost-effective option for your specific situation.