Moving In Together in Japan: The Household Admin Nobody Warns You About

Quick answer

Hi, I'm Miya, and I help newcomers settle into life in Japan. Moving in with someone is supposed to be the warm part, and then you find that the paperwork here has quiet opinions about it. Nothing unkind — just small systems built around one contract, one name, one household. Two unmarried people sharing an address breaks nothing, but a few things have to be said out loud rather than assumed, and the ones people skip tend to come back later.

The short version: check whether your lease allows a second occupant and tell the management company rather than hoping nobody notices; each of you files your own move-in notice at the ward office, and decides there whether you register as one household or two; utilities and internet sit in one person's name even though you both use them; money stays individual; and insurance and hospitals treat an unmarried partner differently from a spouse. Practice varies by ward, landlord and hospital, so confirm the details where you live.

The lease comes before the boxes

Your contract almost certainly names who may live in the flat, and often caps the number of occupants. A place let for single occupancy is exactly that, and a second person moving in permanently changes the contract rather than being a private arrangement between you. People skip this step assuming they will be refused, and usually they are not. Telling the agency is normally unremarkable: a name, sometimes identification or proof of income, occasionally a short review like the original application, and then the contract is updated.

The alternative is worse. An undeclared occupant tends to surface eventually, through a delivery, a neighbour, a renewal or an insurance claim, and by then you are explaining from a weak position; under some contracts it is grounds for refusing renewal. If you are the one moving in, ask what your status on paper will be — a permitted occupant, or a co-tenant who shares the obligations including rent. While you have their attention, ask whether the fire insurance attached to the lease covers your belongings too.

Two move-in notices, one address

The ward office registers people, not couples, so each of you files your own notice even if you go together. Coming from another municipality, you file a moving-out notice (転出届) at the old office, collect the moving certificate (転出証明書), and file a moving-in notice (転入届) at the new one within 14 days. Moving inside the same ward, it is a single change-of-address notice (転居届). Either way the office writes your new address on the back of your residence card, so bring it.

The part that catches people is the household. A 世帯 is an administrative unit, and two people at one address can register as a single household with one householder (世帯主), or as two households sharing an address. For an unmarried partner the relationship recorded is commonly co-resident (同居人), though what a given office can record varies, so ask at the counter what each option changes. It affects whose name appears on the residence record, how notices arrive, and how health insurance is billed. Some municipalities also run partnership declaration systems, so ask if that applies to you.

Two practical things follow. Copies of your residence record (住民票) can be issued showing the other household members or hiding them, so ask for the version that fits when an employer or an immigration procedure wants one. And put both names where couriers can see them, on the mailbox and the intercom: delivery here is matched by name, and a parcel addressed to a name that is not on the door can simply go back to the depot.

Utilities and internet sit in one name

Electricity, gas and water are each contracted by one person, and that person is the account holder — the only one who can change the plan, report a fault, query a strange bill or close the account. Both of you use the service; one of you can talk to the company about it. Decide deliberately who holds which, rather than letting everything land on whoever arrived first, because if that person later moves out, all of it has to be transferred at once.

Internet runs on its own timetable. A new fixed line may need the owner's permission for work on the building, and an installation date weeks rather than days away, so start it the moment the address is confirmed. That contract also carries one name, often with a minimum term and a charge for moving or cancelling it, so read what happens if the named person leaves before you build plans around it.

Then there is splitting, where sharing a home meets a banking system built around individuals. Joint accounts of the kind you may be used to are not generally offered to ordinary customers here, and cards are issued to one named person, so the bill leaves one account and the other settles up. Either spread the contracts so the totals roughly balance, or let one person pay and have the other transfer a share on a fixed day each month. Write down whichever you choose, because direct debits are silent and an imbalance can build for months.

Insurance, hospitals and the parts that aren't shared

Health insurance is where the household choice reappears. Under National Health Insurance, premiums are billed by household, so one household means a single bill covering both of you and separate households mean separate bills; each person still carries their own card. Under employer-based insurance, whether an unmarried partner can be enrolled as a dependent depends on the scheme and the evidence it asks for, so ask the employer's insurance society directly rather than assuming. Hospitals differ too: admission and consent forms usually ask for a family member, and some accept a partner who clearly shares the address while others want a relative.

You can make that easier long before you need it. Name each other as emergency contact wherever forms allow, keep the other's full name and contact details somewhere you carry, and know where a copy of the residence record showing the shared address is kept — often the simplest evidence that you live together. Beyond that, I will be straight with you: sharing an address does not by itself create the legal relationships marriage does, and questions about medical decisions, inheritance or residence status depend on your circumstances and belong with the relevant official body or a qualified professional.

Your number stays yours

Look back and notice what never merged. The ward office registers each of you separately. Every contract carries one name. Hospital forms ask for a person, not a couple. Your phone number works the same way: a verification code for a bank, a utility or a delivery goes to the number attached to that one account, and the courier calls the number given at checkout, not the household. Running two people's admin through one number produces small failures constantly, like a code arriving on the wrong phone.

So if one of you arrived recently and is still borrowing the other's number, fix that before the lease paperwork rather than after. Applying online with your residence card is the normal route, and if your phone takes an eSIM you can often be connected the same day, usually around fifteen minutes from finishing the application. Data matters as much as the number, since most of these forms are filled in from a phone. There is a setup guide here on the site with what you need and the order to do it in, and conditions do change, so please confirm the current terms on the official page before you apply rather than trusting any summary, including mine.