Analysis of 69 Japanese municipalities found communities with higher proportions of dementia supporter trainees (ranging from 2.62% to 44.85% of residents) showed significantly better recognition of dementia consultation services and increased support-seeking for family members with dementia. Each 10-percentage-point increase in supporter coverage correlated with 3.12-point improvements in service recognition scores. However, broader community attitudes and understanding of dementia remained unchanged regardless of supporter density. This represents one of the first municipal-level assessments of Japan's national Dementia Supporter Initiative, which trains citizens to better support people with Alzheimer's and related dementias. The findings suggest a nuanced reality: while trained supporters effectively improve awareness of available resources within their communities, they may lack sufficient reach or influence to shift deeper cultural attitudes about dementia. This has implications for aging societies worldwide grappling with dementia stigma and care coordination. The study's ecological design limits causal interpretation, and as a preprint awaiting peer review, these municipal-level associations require validation through longitudinal research to confirm whether supporter training genuinely drives improved community outcomes.