If you have company health insurance and miss more than 3 days of work because of illness or injury outside of work, you get about two thirds of your pay, for up to 1 year and 6 months.
When you are on sick leave.
Ask your HR department for the form. The doctor fills in one part. 国民健康保険 usually does not have this allowance.
General explanation, for guidance. Rules and amounts change: confirm with the responsible office.