The Real Numbers: 10 Days in Japan

Abstract comparisons don't help you decide. So let's use a concrete example: a solo traveler spending 10 days in Japan — Tokyo, Kyoto, Osaka — using roughly 1GB of data per day. That's maps, messaging, Instagram, and the occasional Google Translate photo. No heavy video streaming.

Here's what each connectivity option costs for that exact trip:

Option 10-Day Cost Setup Hotspot
AT&T International Day Pass ($12/day) $120 Auto-activates on use Limited
T-Mobile International ($15/day) $150 Auto-activates on use 512MB/day
Japan Pocket Wi-Fi rental $80–$100 Airport pickup + return Yes (separate device)
Local Japan SIM (Narita Airport) ¥3,000–¥4,500 (~$20–$30) 30+ min queue at airport Sometimes
lamasim Japan eSIM (10GB) $8.48 60 seconds, pre-trip Included

The lamasim eSIM costs $8.48 for 10GB, which is more than enough for a 10-day trip. Compared to AT&T's Day Pass at $120, you're saving $111.52 on a single trip. If you travel internationally three times a year, that's over $300 in savings annually.

Convenience Comparison

Factor Carrier Roaming Local SIM lamasim eSIM
Setup time Instant (auto) 30–60 min at airport 60 sec, pre-trip
Keep your home number active Yes No (SIM replaced) Yes
Physical SIM required No Yes No
Works before landing Yes No Yes
Risk of losing SIM None High (tiny card) None
Hotspot/tethering Limited or extra charge Sometimes included Always included
Multi-country coverage Yes (at high cost) One country only Yes (regional plans)

When to Use Each Option

Use Carrier Roaming If...

  • You're traveling for 1–2 days only and the day pass math works out
  • Your carrier offers a genuinely good international plan (some do — check carefully)
  • You're in a hurry at the airport and didn't plan ahead
  • Your phone doesn't support eSIM (check with Settings → About → EID)

Watch out for: "International plan" fine print — many US carriers throttle speeds to 128Kbps after a daily data cap. That's barely enough for text messages, not maps.

Use a Local SIM If...

  • You're staying in one country for an extended period (3+ weeks)
  • You need a local phone number for calling hotels, restaurants, or services
  • Your phone doesn't support eSIM
  • Local SIM prices at your destination are exceptionally competitive (e.g., India, Southeast Asia)

Watch out for: Replacing your SIM means losing access to your home number during your trip. You'll miss calls and, crucially, two-factor authentication SMS codes from your bank, email provider, and social media accounts.

Use lamasim eSIM If...

  • You want the lowest price without the airport hassle
  • You need to keep your home number active (for 2FA and incoming calls)
  • You're visiting multiple countries
  • You want hotspot included so you can tether a laptop
  • You like planning ahead (buy at home, install at home, land ready)

Speed and Coverage Differences

One misconception about travel eSIMs is that they offer slower speeds or weaker coverage than local SIMs. This isn't true for lamasim. We provision directly onto the same local carrier networks as the physical SIMs sold at the airport. A lamasim Japan eSIM uses the same NTT Docomo 4G/5G infrastructure as a physical Docomo SIM — there is no speed or coverage difference.

Carrier roaming, by contrast, often involves network deprioritization. When a roaming device connects to a local tower, it may be given lower priority than local subscribers during peak times, resulting in slower speeds even on a nominally "full 4G" connection.

Setup Time Comparison: Real Timings

  • Carrier Roaming: ~0 minutes — activates automatically when your phone connects. But you're paying $10–$15/day from the second it activates.
  • Local SIM at Airport: 30–90 minutes — queue at the kiosk, show passport, activate the SIM, wait for it to register on the network, swap your existing SIM (and store it somewhere safe).
  • lamasim eSIM: ~60 seconds to install at home. Zero minutes at the airport — your data is active the moment you land.

Environmental Impact: No Plastic SIM Waste

This isn't a marketing point — it's a genuine environmental consideration. The global SIM card industry produces approximately 4.5 billion physical SIM cards per year. Most are used briefly and discarded. SIM cards are made from PVC plastic and contain small amounts of precious metals — they're difficult to recycle and largely end up in landfill.

eSIMs eliminate the physical card entirely. No plastic, no packaging, no shipping. If you travel four times a year and switch to eSIM, you're removing 4+ plastic SIM cards from circulation annually. Scaled across millions of travelers, that's a material impact.

The Verdict: Which Should You Use?

For the vast majority of international travelers, a travel eSIM like lamasim is the clear best choice:

  • It's 10–20x cheaper than carrier roaming day passes
  • It's cheaper than airport local SIMs in most destinations
  • You keep your home number active
  • You can set it up before you leave, so you're online the moment you land
  • Hotspot is included — tether your laptop without extra fees
  • No plastic waste

The only scenario where a local SIM beats an eSIM is a long stay (3+ weeks) in a single country where you need a local number. Even then, a lamasim eSIM plus a cheap local calling app (WhatsApp, Skype) covers most use cases.

See plans and pricing for your destination at lamasim.com/destinations.

Frequently Asked Questions

Is carrier roaming ever a good deal?

Occasionally. Some carriers — especially budget MVNOs — include international data in their base plans. Google Fi, for example, includes basic international data in most plans. If your carrier does this, roaming can be the most convenient option. Check your current plan carefully before assuming roaming is expensive.

Can I use lamasim for calls, not just data?

lamasim eSIMs are data-only plans. For calls, keep your home SIM active and use data-based calling apps like WhatsApp, FaceTime, Skype, or Google Voice over your lamasim data connection. This is how most travelers handle calls abroad — it's cheaper than any voice roaming plan.

What happens if I go over my lamasim data limit?

Your data connection pauses. You won't be charged overage fees — data simply stops until you top up. You can top up instantly in the lamasim app with no need to reinstall anything.

Does the local SIM option work in Japan for tourists?

Tourist SIMs in Japan are data-only — Japanese law requires proof of residency for SIMs with voice calling capability. So the local Japan SIM option is effectively equivalent to a travel eSIM in terms of functionality — just more expensive and slower to set up.

How do I know if my phone supports eSIM?

On iPhone: Settings → General → About — look for an "EID" number. On Android: Settings → About Phone — look for "EID." If the EID field exists, your phone supports eSIM. Alternatively, check our compatibility checker on the destinations page.