The Health and Medical Service Act for the Aged stipulates that the "Health and Medical Service System for the Aged" provides benefits in the form of medical treatment to all elderly persons aged 75 or over (65 or over in cases of bedridden persons and others with similar conditions and 70 or over in cases of persons born before September 30, 1932). Therefore, the Health and Medical Service System for the Aged takes over benefit provision from Health Insurance Societies when insured persons and their dependents reach the ages specified above.
Elderly persons aged 75 or over pay the equivalent of 10% of their medical expenses whether they are treated as outpatients or inpatients.
Due to revision of the Health and Medical Service System for the Aged, beginning April 2008 a new Medical Care Service System for the Aged will be established.
See here for details. >> "Health insurance after retirement #Establishment of a new medical care service system for the aged"

10% patient cost-payment

When persons covered under the Health and Medical Service System for the Aged receive medical treatment, they present their Health Handbook (with medical beneficiary identification attached) and insurance card to a medical institution authorized to treat patients covered by the health insurance system.
As is the case with elderly persons aged 70 years or over, in this case patients pay 10% of their medical costs at the time they receive treatment. In addition, if they are hospitalized, patients pay a standard charges for their meals (260 yen per meal up to a maximum of 780 yen for 3 daily meals).
Note that patients must pay meal and accommodation expenses incurred during hospitalization in medical treatment facilities. Insurance will cover the standard amount of living expenses required (1,700 yen per day).
See here for the cost-sharing maximum amounts, etc. >> "Elderly persons aged 70 or over pay 10% or 30% of medical costs, depending on their income　#Cost-sharing maximum amount for the elderly"

Benefits other than those for medical treatment are provided by the Health Insurance Society

Although medical-related benefits are no longer available from the Health Insurance Society, insured persons and their dependents are not disqualified from receiving other benefits and health activities, which will continue to be provided by the Health Insurance Society.

Administration of the Health and Medical Service System for the Aged

The Health and Medical Service System for the Aged is administered by municipal governments (meaning cities, towns and villages plus the 23 wards of Tokyo). All medical care insurers-including Health Insurance Societies and mutual aid associations-share the cost of its administration (the state and local governments bear part of the expenses as well). The Service offers (1) medical treatment to persons aged 75 or over (65 or over in cases of bedridden persons and 70 or over in cases of persons born before September 30, 1932), (2) health (and health management) activities for persons aged 40 or over, and (3) home-visit nursing care for the elderly.
Service windows are located at municipal government offices.