To cite package ‘jpmapdata’ in publications use:

  Horiuchi Y (2026). _jpmapdata: Boundary Data for Japan Maps_. R
  package version 0.1.0,
  <https://CRAN.R-project.org/package=jpmapdata>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {jpmapdata: Boundary Data for Japan Maps},
    author = {Yusaku Horiuchi},
    year = {2026},
    note = {R package version 0.1.0},
    url = {https://CRAN.R-project.org/package=jpmapdata},
  }