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Hi, I'm Hiroshi — a blogger in my 50s based in Sagamihara, Japan.
About a year ago, I wrote this:
"After switching to IIJmio, our family of four pays around $30/month for smartphones."
That wasn't a lie. But it wasn't entirely accurate either.
After pulling every single monthly bill from the past year, the real average came out to about $34/month.
A $4 difference.
You might think that's nothing. And honestly, it is. But I felt I owed you the real numbers — so here they are.
Who this is for
- Anyone considering a switch to a budget SIM in Japan
- Families looking for the real cost — not the marketing number
- People in their 40s or 50s who want to quietly cut fixed costs
Bottom line (upfront)
$34/month wasn't a failure. It was still one of the best financial decisions our family has made.
The Honest Data: 12 Months of Real Bills
Here's every bill from April 2025 through March 2026. No cherry-picking.
| Month | Amount (USD) |
|---|---|
| Apr 2025 | $38.05 |
| May 2025 | $36.00 |
| Jun 2025 | $30.94 |
| Jul 2025 | $34.44 |
| Aug 2025 | $30.67 |
| Sep 2025 | $30.34 (lowest) |
| Oct 2025 | $34.97 |
| Nov 2025 | $33.68 |
| Dec 2025 | $33.34 |
| Jan 2026 | $34.75 |
| Feb 2026 | $33.42 |
| Mar 2026 | $35.08 |
12-month average: approx. $34/month. Annual total: approx. $405.
Lowest month: $30.34 (September 2025). Highest: $38.05 (April 2025). Spread: about $7.70.
Eight months came in above $33. Four months stayed under $32. All of them stayed well under what we used to pay.
Why the Bill Fluctuates
The reason isn't random. It comes down to one variable: which large-data plan we choose each month.
Here's our family's setup:
- 5GB plan × 3 people ($6.63/person/month)
- Large-data plan × 1 person (switched between 25GB and 35GB depending on the month)
| Plan | Monthly cost (USD) |
|---|---|
| 5GB plan | $6.63 |
| 25GB plan | $13.40 |
| 35GB plan | $18.09 |
The base for 3 people on 5GB is about $19.89/month. The one high-usage person accounts for the remaining $13–$18, depending on the month.
When they switch up to the 35GB plan, the bill jumps by about $4.70. That's the entire "mystery gap" explained.
Think of it like a utility bill — it varies a little, but it never spikes unpredictably. Once I stopped thinking "what's the monthly number?" and started thinking "what's the annual number?", the anxiety disappeared.
Still an Unbeatable Deal — Here's the Math
Let's put $34/month in context.
A family of four on a major Japanese carrier typically pays somewhere between $121 and $168 per month.
| Monthly | Annual | |
|---|---|---|
| Major carrier (estimate) | $121–$168 | $1,452–$2,016 |
| IIJmio (actual) | $34 | $405 |
| Difference | $87–$134 | $1,047–$1,611 |
That's $1,000–$1,600 per year back in our pocket. Every single year.
A $4 monthly variation feels a lot smaller when the annual gap is measured in four figures.
Over the year, the cost per GB worked out to about $0.48. Compared to major carriers, that's 4–7 times more efficient.
The Quiet Features I Didn't Expect to Love
Before switching, I had a nagging worry: "What if budget SIM turns out to be inconvenient?"
After 12 months, I can say: the inconveniences I feared never showed up. What did show up were features I hadn't expected to appreciate.
Data rollover
Unused data carries over to the next month automatically. No more frantically watching YouTube videos at the end of the month to "use up" what's left. Leftover data just becomes a head start for next month.
Data sharing
All four family members share a data pool. At the start of each month, we have roughly 70GB available across the family. If one person uses more, another person's leftover naturally covers the gap.
Multi-line discount (mio discount)
When multiple lines are on the same account, a discount kicks in. The more family members you bring over, the more each line benefits.
How We Actually Run It Month to Month
Nothing fancy. Just three habits that take about two minutes a month.
Check the plan at the end of the month
The heaviest data user in the family looks at their usage and decides whether next month calls for 25GB or 35GB. If there's a trip or a busy stretch coming, go up. If it's a quiet, stay-at-home month, drop down. That one decision saves or costs about $4.70.
Keep everyone on data share
All four lines stay linked in the same data pool. Every month starts with ~70GB available. No manual management needed — it just works.
Ignore the rollover counter
Unused data rolls over automatically. I never check how much carried over. It's just a buffer that quietly helps. That's the part I appreciate most — one less thing to think about.
What Phone Bills Look Like in Your 50s
Fixed costs are the best kind of savings because they compound without effort.
Cutting $10 from your grocery budget requires discipline every single week. Switching phone plans requires effort once — and then it just keeps saving.
In my 50s, I've come to prefer that kind of quiet, structural saving over white-knuckle budgeting.
The $1,000+ we save each year can go toward NISA, iDeCo, or just a little more breathing room. A few years of that compounds into something meaningful.
Before chasing high-return investments, fix your fixed costs. It's unsexy advice. But it works.
Closing Thoughts
I said $30/month. The truth was $34/month.
For a moment, I thought I'd gotten it wrong. But when I laid out all 12 months side by side, what I saw was: consistent, predictable, and genuinely cheap.
Budget SIM isn't a perfect tool. It's a tool that rewards a little monthly attention with a lot of annual savings.
If you're on the fence, try it for one month. The worst case is that you go back. But almost nobody goes back. That gap is real.
You don't need dramatic savings. Just quiet ones that work every month for the rest of your life.
#IIJmio #MVNOJapan #FamilyPhonePlan #FixedCostReduction #FrugalLiving #LifeIn50s #JapanSIM #SmartSaving #PhoneBillHack
Related Posts
How We Cut Our Family Phone Bill with IIJmio | The original article — before and after switching
Trimming Fixed Costs in Your 50s | What to do with the money you free up
NISA or iDeCo First? A Guide for People in Their 50s | Putting the savings to work