How to Keep Your Phone Number Without Losing It: povos 180-Day Rule vs. Flat-Rate SIMs

Here's the bottom line: if your only goal is keeping your number for as little as possible, povo2.0 (¥0 base fee plus one small task every six months) is hard to beat. If you'd rather set it and forget it, a low-cost flat-rate voice SIM (such as Nihon Tsushin, mineo, or HIS Mobile, roughly ¥250–¥290 a month) makes more sense. The cheapest route carries a management risk — forget to make a purchase every 180 days and your number can lapse — while flat-rate plans nearly remove that risk in exchange for a few hundred yen each month. There's no single right answer. The way to avoid regret is to ask yourself one thing: are you someone who can stay on top of reminders, or someone who simply doesn't want the hassle? This article walks through how to keep a number from lapsing and offers a neutral way to choose between the two approaches. Prices and terms change, so always confirm the latest details on each provider's official site (figures are approximate and tax-included, as of June 2026).

Why a phone number can quietly lapse in the first place

A phone number stays yours as long as the line contract is active. The catch is that the plans built to cut costs to the bone tend to come with a condition: leave the line completely unused and unpaid for a set period, and service is suspended — and eventually the number disappears. This is especially common with ¥0 base-fee plans. A provider can't keep an unprofitable contract alive indefinitely, so it asks for some paid activity within a fixed window.

In other words, "cheapest" and "risk of lapsing" are a trade-off. Choose on price alone and you may discover, six months later, that your number is gone — and suddenly SMS verification for banking, social accounts, and various logins stops working all at once. The shortcut is to first decide which type of person you are. If you'd like to see your options for keeping a number side by side, our phone number and SMS guides are a good companion read.

povo's "180-day rule" and how to keep your number alive

The appeal of povo2.0 is that you can hold a line with a ¥0 base fee. But there's an important condition: if you don't purchase a paid topping (such as added data) within 180 days, your line is subject to suspension and your number to cancellation. The key point is that you can't keep it alive at a true ¥0 forever.

Flip that around, though, and all it takes is buying the cheapest topping once every six months to keep your number. Averaged out, the upkeep works out to roughly ¥40–¥60 a month — about as low as number retention gets (based on buying the cheapest topping once every six months; approximate, as of June 2026 — confirm the latest on the official site).

Three habits that prevent a lapse

• Put a calendar reminder well before the 180-day mark: instead of cutting it close, set the reminder around 120–150 days after your last purchase to stay safe.
• Schedule the next purchase the moment you buy: right after you buy a topping, register the date of your next one. It's far harder to forget that way.
• Note the day you used it: keep a record of any data you used or bought, and you'll never be unsure where you stand.

For people who can keep this rhythm going, povo is the strongest choice for number retention. On the other hand, if you're not confident you'll stick with calendar reminders, the flat-rate option below will feel far more reassuring.

The peace of mind of a flat-rate SIM that won't vanish

With a low-cost voice SIM that charges a fixed monthly amount, there's almost no chance of forgetting a purchase and losing your number. Think of it as buying away the management hassle for a few hundred yen. Here are some representative options, laid out neutrally (approximate, tax-included, as of June 2026 — confirm the latest on each official site).

• Nihon Tsushin SIM "Gouriteki Simple 290": ¥290/month for 1GB. Extra data is ¥220 per 1GB, with no minimum term or cancellation fee. A well-balanced "hands-off peace of mind" option.
• mineo "Mineo Mai-soku Super Light": ¥250/month. At a maximum of 32kbps it's very slow and not suited to normal browsing, but if you're happy to limit it to calls and SMS verification only, it's among the cheapest. A separate initial fee applies.
• HIS Mobile "Jiyu Jizai 2.0": ¥290/month (when usage is under 100MB, tax-included). Low per-call rates and 5G support.
• irumo 0.5GB: ¥550/month. Backed by a stable, mainline network — a good fit for those who value reassurance (confirm the latest pricing on the official site).

What they all share is a small risk of losing your number to a forgotten purchase, simply because they're flat-rate. Rather than asking which is "better" or "worse," it's easier to decide based on whether you can live with slow speeds, or you'd like some everyday usability too.

Cheapest possible vs. hands-off peace of mind: a quick comparison

Type	Example	Approx. monthly number-retention cost	Management effort	Best for
Cheapest possible	povo2.0	Approx. ¥40–¥60 equivalent (one purchase every six months)	One small task every 180 days	People who can keep up with calendar reminders
Reassuring, flat-rate	Nihon Tsushin / HIS	Around ¥290/month	Almost none	People who want hassle-free retention
Verification-only, no frills	mineo Mai-soku SL	¥250/month	Almost none	People who only need calls and SMS verification

* Figures in the table are approximate and tax-included, as of June 2026. Prices and terms change, so check each provider's latest official listing before signing up.

Splitting data off to Bloomy: an "add-on" way of thinking

Once you've made number retention cheap, there's one more move: a dual-SIM setup where you hold your data separately. Leave calls and SMS verification to your current number (the low-cost voice SIM), and handle data with a cost-efficient data-only eSIM — your number stays exactly as it is, so it's a pure "add-on" where no one loses out.

One important premise here: Bloomy plans are, by design, data-only. They don't include a phone number, SMS, or voice calls. That's precisely why the combination works so naturally: keep your number on your existing voice SIM, and simply add Bloomy for data. App-based calls such as WhatsApp may be usable in environments where data is available. Note that communication quality varies with the local network, your device, and your area.

In terms of cost, the idea is to hold your number for a few hundred yen a month while choosing exactly the data you need from Bloomy's capacity plans. You can check current data capacities and pricing in the table below; final pricing is shown at the time of purchase, so please confirm it there.

[bloomy_price_table]

For example, pairing "number = a flat-rate voice SIM (¥290/month) + data = a 20GB-class Bloomy plan" tends to land somewhere in the low ¥2,000s per month as a rough guide. In some cases that comes out lower than a major mainline brand's 20GB tier (roughly ¥4,000+/month without discounts) (based on a major mainline 20GB plan with no discounts applied; as of June 2026). That said, this isn't a promise that everyone will pay half or that everyone will save — the result depends on your current contract and how much data you use. Take it in the spirit of "depending on your situation, there may be an option worth reviewing."

A voice SIM that includes a small data allowance also doubles as a backup if your eSIM ever runs into trouble — reassurance on two fronts. Bloomy plans are governed by a fair-use policy.

Which type are you? A quick decision guide

• Managing a calendar or reminders doesn't bother you → keep your number cheaply with povo. One small task every six months, around ¥40–¥60 a month.
• You just don't want to forget or think about it → a flat-rate SIM like Nihon Tsushin or HIS. A few hundred yen a month for hands-off peace of mind.
• You only need calls and SMS verification → a no-frills option like mineo Mai-soku SL, plus exactly the data you need from Bloomy.

Whichever type you are, the idea of splitting data off to Bloomy works the same way. To see whether a data-only eSIM will work on your device, it's worth checking our eSIM compatible devices page first (confirm combinations in advance, such as physical SIM + eSIM, or two eSIM lines on iPhone 13 and later).

How the setup flows, and what to do if you get stuck

The basics of dual SIM are simple: set your default voice line to the low-cost voice SIM, and mobile data to Bloomy's data-only eSIM. Your number stays the same, and only data runs through Bloomy. We've gathered the specific steps in our setup guide. If switching doesn't go smoothly or data won't connect, don't panic — our FAQ is also worth a look.

Find a data plan with Bloomy

If you want to keep your number as-is and just rethink your data, you can choose a plan by capacity and duration from our eSIM comparison page. It's an easy setup to use whether you're staying in Japan long-term, traveling, or simply trimming your everyday bill. For more ways to save at home and abroad, see our smartphone bill savings guide.

Summary

The cheapest way to keep a number is povo (one small task every six months); the hassle-free, reassuring route is a flat-rate voice SIM. The key to preventing a lapse is choosing between two strategies: build a system you can manage in advance, or remove the hassle entirely with a flat rate. On top of that, splitting data off to Bloomy's data-only eSIM may let you keep your number exactly as it is while reviewing only your data costs. Remember that Bloomy is data-only (no phone number, SMS, or voice calls), is governed by a fair-use policy, and that communication quality varies with the local network, device, and area. Prices and terms change, so confirm the latest on each provider's official site and on Bloomy's comparison page before signing up (figures approximate and tax-included, as of June 2026).