Japan has the highest proportion of elderly persons in the world, and the number of those living with dementia is currently around 5.5 million (16% of individuals aged ≥65 years). Estimates indicate that this will increase to 7 million (20% of individuals aged ≥65 years) by 2025. Dementia is defined as cognitive impairment due to various types of brain disease that disrupt activities of daily living (ADL). However, clinical features of dementia can be more and more complex, including physical, mental, and social disability, accompanied by social isolation, economic issues, caregiver burdens, and so on. The complexity of dementia is the main factor that disrupts everyday life in communities. To minimize complexity, we have developed a program that provides comprehensive geriatric assessment (CGA), facilitates access to diagnosis, and coordinates appropriate integrated care for persons living with dementia. The Dementia Assessment Sheet for Community-based Integrated Care Systems (DASC)-21 is a tool comprising 21 items with which to assess cognitive function, instrumental ADL, and basic ADL. The DASC-21 uses a cut-off of 31/30, which discriminates dementia from non-dementia with 91.3% sensitivity and 82.5% specificity. The Initial-Phase Intensive Support Team was launched in 2014 as a national health program for individuals with early-stage dementia. The DASC-21 is essentially applied nationwide within this program. We are presently investigating how to create dementia-friendly communities through dialogue with people living with dementia and caregivers, applying the DASC-21 for CGA, and coordinating integrated care with inter-professional collaboration.