Flag of Yamanashi Prefecture. Published to December 1, 1966.
Own work using: https://www.pref.yamanashi.jp/somu/shigaku/reiki/reiki_honbun/a500RG00000136.html Notes: Although the law says the background is violet, the official specification given by the Yamanashi Prefectural Government states that it is  "Magenta 100 + Cyan 40 + Yellow 60". See also https://www.pref.yamanashi.jp/chiji/dekigoto/0111/20.html and https://www.pref.yamanashi.jp/gikaisom/kids_9.html.
UnreifeKirsche, Mike Rohsopht