Most car rental companies in Matsumoto require a credit card for the rental process. It serves as a form of payment and security deposit. If you don't have a credit card, some rental companies may accept a debit card or allow you to pay with cash, but additional requirements and restrictions may apply. It's best to check with the specific rental company for their payment options.

When renting a car in Matsumoto, you will typically need to present the following documents:
- A valid driver's license from your home country or an International Driving Permit (IDP)
- A valid passport or identity card
- A credit card in the driver's name for payment and security deposit
- Some rental companies may also require additional identification or proof of address. It's best to check with the specific rental company for their document requirements.

Insurance coverage for a rental car in Matsumoto may vary depending on the rental company and the type of insurance you choose. Most rental companies offer basic insurance coverage, also known as Collision Damage Waiver (CDW), which typically has an excess/deductible amount that you would be responsible for in case of damage or theft. You may also have the option to purchase additional insurance coverage to reduce or eliminate the excess amount. It's recommended to review the insurance options and terms with the rental company before making a reservation.

Some rental companies in Matsumoto may allow you to cross borders with a rental car, while others may have restrictions or additional fees. It's important to check with the specific rental company beforehand if you plan on crossing borders during your rental period. Additionally, you may need to inform the rental company about your travel plans and obtain any necessary documentation or permits for driving in other countries.

In case of an accident or breakdown with a rental car in Matsumoto, it's important to follow these steps:
1. Ensure your safety and the safety of others involved. Call emergency services if necessary.
2. Contact the rental company immediately to inform them about the situation and follow their instructions.
3. If there are no injuries and the car is still drivable, move it to a safe location if possible.
4. Take photos of the accident or damage and gather any relevant information, such as the other party's contact and insurance details.
5. Fill out an accident report or incident form, if provided by the rental company.
6. Depending on the severity of the accident or damage, you may need to involve the local authorities or insurance companies.
It's important to familiarize yourself with the rental company's policies regarding accidents and breakdowns before renting a car.