Do You Need a Car Seat in Japan? Under 6 Is the Law — Okinawa Rentals

Yes. In Japan, the driver must use a child seat for a child under six years old. That rule applies when you rent a car in Okinawa as well as when you drive your own vehicle.

The part most guides leave out is that "one child seat" is not a specification. Okinawa rental companies stock different products with different size limits, and the same category name does not mean the same seat. A booking that only says "child seat: 1" can still produce a seat your child does not fit.

This guide gives you the size ranges four companies actually publish, and a message you can copy and send to confirm your own booking. If you only want the message, it is under "The message to send when you book" below, written in Japanese, with a filled-in example and an English translation of every line.

The short version

• Reserve the child seat when you reserve the car, not after arrival.
• Send the child's age, height and weight — not just the number of seats.
• Ask whether the booked vehicle still fits everyone and the luggage once seats are installed.
• A child turning six does not automatically fit an adult seat belt correctly.
• At pickup, check the product label, installation and harness before driving away.

What Japanese law actually says

Japan's road traffic law states that a driver must not drive while carrying a child under six who is not using a child restraint. The official term is 幼児用補助装置 (*yōji-yō hosoku sōchi*), a child restraint device, and 幼児 (*yōji*) means a child under six.

Limited exceptions exist, mainly where a medical condition makes restraint use unsuitable for treatment, plus other circumstances defined by ordinance.

The point most English guides miss is what the National Police Agency says about older children: even for a child aged six or over, a child seat should still be used when body size means the seat belt cannot be worn correctly. JAF uses roughly 150 cm as a practical reference height for moving out of a booster.

So age six is the legal line, not the safety line. Do not assume 150 cm is the limit of every rental product either — several rental seats stop well below it.

The three kinds of seat, in plain terms

Japanese rental companies use three names. They are not interchangeable, and the difference is physical, not just a label.

• Infant seat — a carrier-style seat that faces backwards, for a baby who cannot sit up unsupported.
• Child seat — faces forwards and has its own built-in five-point harness, like a small racing harness over the shoulders and between the legs. For toddlers and preschoolers.
• Junior seat (also called a booster) — a cushion, sometimes with a back, that raises the child so the car's own adult seat belt crosses their shoulder and hips in the right place. It has no harness of its own.

You will also see ISOFIX. That is simply a pair of metal anchor points built into the car, which the seat clips onto directly instead of being strapped down with the car's seat belt. It is quicker and harder to fit wrongly. Not every car or seat has it, which is why it is worth asking.

Start with your child's height

Measure your child before you read the next table. Height decides the seat far more often than age does.

Japanese companies publish everything in centimetres and kilograms, so both are given below. To convert your own figures: 1 inch = 2.54 cm, and 1 pound = 0.45 kg. A quick way to check yourself — a child of 3 ft 3 in is right around 100 cm, which is the height that causes the most confusion.

If your child is anywhere near 100 cm, the section after next matters more than anything else on this page.

What four Okinawa companies actually stock

These four are among the companies most often used by visiting families. OTS, Nippon and Toyota are large national chains with counters serving Naha Airport; Okinawa Rent-a-Car is a local Okinawan operator. Booking sites and comparison platforms usually resell one of these.

These are the published figures as of August 8, 2026. They change, so confirm for your own dates. Fees are per rental, not per day, and ¥1,100 is roughly the price of a casual lunch in Japan — small enough that it should not decide which company you choose.

Three things follow from this table.

The same seat name has different limits. A child measuring 105 cm is inside Nippon's child range, but has already passed OTS's 100 cm child limit and would need an OTS junior seat — which OTS lists from age four. Around 100 cm, three different categories overlap. If your child is near that height, the category you are given depends on which company you booked.

The fee ranges from free to ¥1,650. Okinawa Rent-a-Car includes seats at no charge, but publishes no size ranges at all, which makes asking mandatory rather than optional.

Installing seats shrinks the car. Toyota's own accessory page notes that a three-row vehicle fitted with a child seat comfortably takes one adult plus one child seat in that row. A seven-seater on paper is not a seven-seater once two child seats are in.

None of these four pages tells you what information to send when you book. That is the gap this next section fills.

The message to send when you book

Send it at the same time you reserve the car, not after you arrive.

Write it in Japanese. Most Okinawa companies have English pages, but branch staff confirm details in Japanese, and several handle enquiries by LINE or a web form rather than email — Okinawa Rent-a-Car lists a phone number, LINE and a contact form, with no public email address at all.

You do not need to read Japanese to use this. Here is what every line says.

Then copy the block, fill in the blanks, and paste it into the booking notes field, an email, or a LINE message.

You do not need to worry about writing perfect Japanese. Airport-branch staff deal with visiting families every day, and a clear, polite enquiry from a foreign customer is completely ordinary. The wording below follows the normal Japanese convention for a first message to a company: greet, say why you are writing, then list the questions.

初めてご連絡いたします。
チャイルドシートについて
お伺いしたく、ご連絡いたしました。

予約者名：
予約番号：
利用日：　　　　〜
出発店舗：

同乗する子どもの情報
・1人目：　歳　か月
　身長　　cm／体重　　kg
・2人目：　歳　か月
　身長　　cm／体重　　kg

お伺いしたいこと
1. 上記の子どもに適合するチャイルド
   シートの種類と、実際の適用身長・
   体重の範囲を教えてください。
2. 予約した車種にシートを取り付けた
   状態で、大人　名が乗車し、
   スーツケース　個とベビーカー　台を
   積むことは可能でしょうか。
3. ISOFIX対応のシートはありますか。
   シートベルト固定のみでしょうか。
4. チャイルドシートの料金と、
   取り付けを店舗で行っていただける
   かどうかを教えてください。

お手数をおかけしますが、
よろしくお願いいたします。

What it looks like filled in

A family of two adults and two children, collecting a car at Naha Airport:

初めてご連絡いたします。
チャイルドシートについて
お伺いしたく、ご連絡いたしました。

予約者名：CHEN WEI
予約番号：ABC123456
利用日：2026年10月3日〜7日
出発店舗：那覇空港

同乗する子どもの情報
・1人目：4歳2か月
　身長 102 cm／体重 16 kg
・2人目：1歳0か月
　身長 74 cm／体重 9 kg

お伺いしたいこと
1. 上記の子どもに適合するチャイルド
   シートの種類と、実際の適用身長・
   体重の範囲を教えてください。
2. 予約した車種にシートを取り付けた
   状態で、大人 2 名が乗車し、
   スーツケース 2 個とベビーカー 1 台を
   積むことは可能でしょうか。
3. ISOFIX対応のシートはありますか。
   シートベルト固定のみでしょうか。
4. チャイルドシートの料金と、
   取り付けを店舗で行っていただける
   かどうかを教えてください。

お手数をおかけしますが、
よろしくお願いいたします。

The older child here is 102 cm, which is exactly the case worth asking about: inside one company's child-seat range, past another's.

Shorter version for LINE

初めてご連絡いたします。
チャイルドシートについて
お伺いしたく、ご連絡いたしました。
予約番号：　　　／利用日：
子ども：　歳　か月
身長　cm・体重　kg（　名）
1. 適合するシートの種類と
   適用範囲を教えてください。
2. 予約車種にシートを付けた状態で、
   スーツケース　個と
   ベビーカー　台は積めますか。
3. 料金と取り付け対応の有無も
   教えてください。
よろしくお願いいたします。

What you are asking, in English

1. Which seat type fits our child, and what is that seat's actual height and weight range?
2. With those seats installed in the vehicle we booked, can it still carry our adults, suitcases and stroller?
3. Do you have ISOFIX seats, or is it seat-belt installation only?
4. What is the fee, and will staff install the seat?

Each question maps to a real failure. Question one exists because category names differ between companies. Question two exists because installed seats reduce usable space. Question three affects how long pickup takes and who does the work. Question four matters because the price ranges from nothing to ¥1,650, and most companies place installation responsibility on the driver.

These templates are compiled from the companies' own published information. Treat the reply from your rental company as the authority for your booking.

What if they reply in Japanese?

They probably will, and that is fine. Paste the reply into any translation app and it will make sense, because the answer is mostly numbers and product names.

These are the words that carry the actual answer.

If a reply is genuinely unclear, it is completely normal to write back with 英語でご回答いただけますでしょうか。 — "could you reply in English?" Staff at airport branches deal with visitors all day.

The two answers you must not leave vague are the seat's actual height and weight range, and whether your luggage still fits with the seats installed. If either comes back without numbers, ask again.

Can you arrange a seat after arriving?

Do not plan on it. Stock can run out, and a company may decline to release the car when a child under six has no reserved seat and the family has not brought one.

Fees and rules differ by company. Check the policy on the same rental page used for your booking rather than applying one company's practice to all of Okinawa.

Six checks before leaving the rental lot

1. Match the seat category to your reservation and to the reply you received.
2. Read the height and weight limits printed on the actual seat, not the website.
3. Install it in a rear seat where possible and follow the product instructions.
4. Confirm the seat belt or ISOFIX connectors are routed and locked correctly.
5. Put the child in the seat and check harness height, tension and twisted straps.
6. Touch the buckle before seating the child — metal parts get very hot in Okinawa.

Japan's transport guidance warns against placing a rear-facing infant seat in front of an active passenger airbag. If anything is unclear, ask staff to show you the manual or the installation points before you leave.

Should you bring your own child seat?

Bringing your own gives you a familiar product and a known size range. It also adds airport and shuttle handling.

Check before deciding:

• the airline's baggage and packaging rules;
• whether the seat suits the booked vehicle;
• whether it uses a seat belt or ISOFIX installation;
• how you will move it with your other luggage between the terminal and the rental office.

Renting is simpler when the company can confirm a suitable model — which is exactly what the message above is for. Bringing your own makes more sense when fit or familiarity matters more than carrying less.

Frequently asked questions

Does a six-year-old still need a booster seat in Japan?

The legal requirement covers children under six. A child aged six or over should still use an appropriate junior seat if the adult belt does not sit correctly across the shoulder and pelvis, which is what the National Police Agency advises. Ask the rental company for a model that fits your child's actual height.

Is a child seat included with an Okinawa rental car?

It depends on the company. Okinawa Rent-a-Car lists child seats as free. OTS and Nippon list ¥1,100 per seat, and Toyota lists ¥1,650 for child and infant seats and ¥1,100 for a booster. Confirm the current price before payment.

My child is around 100 cm. Which seat will I get?

That height sits on the boundary between categories, and the answer differs by company. At OTS, 100 cm is the top of the child seat range. At Nippon, the child mode runs to 105 cm while the junior seat starts at 100 cm. Send the exact height and weight and let the company specify the product.

Will rental staff install the seat?

Policies differ, and several companies state that installation is the customer's responsibility. Even when staff help, check the final installation and the child's harness yourself before leaving.

Can two child seats fit in a small rental car?

Sometimes, but comfort and luggage space become the problem before seat count does. Toyota notes that a three-row vehicle with a child seat installed comfortably seats one adult plus that seat in the row. Give the company your full passenger, seat and luggage count and ask them to confirm the vehicle class.

Can I put a rear-facing infant seat in the front passenger seat?

Do not place a rear-facing seat in front of an active airbag. Use the rear seat and follow the seat and vehicle instructions.

Plan the base before the driving days

A correctly fitted seat is one part of a workable self-drive trip. Long drives still need breaks and a sensible hotel location. If you have not chosen a base yet, compare Naha, central Okinawa and Motobu for a family stay.

Sources and update note

Rental figures in this guide were checked on August 8, 2026 against each company's own published pages. Prices, seat models and policies change, so confirm with your rental company before travel. The Japanese message templates are compiled from those published sources; they are a starting point for your enquiry, not a guarantee of what any company will supply.

• Japan National Police Agency: Child seats
• JAF: Choosing a child seat that fits
• Japan Ministry of Land, Infrastructure, Transport and Tourism: Child seats
• VISIT OKINAWA JAPAN: Rental Vehicles in Okinawa
• OTS Rent-a-Car: Child Safety Seat
• Nippon Rent-A-Car: Child Seat Information
• Toyota Rent a Car: Accessories
• Okinawa Rent-a-Car