Floating around the murky regions of digitized Unicode values are anywhere between 60 and 100 yūrei-moji — literally, “ghost characters” — haunting the Japanese kanji lexicon.
One such example is 彁 (pronunciation unknown). Unlike 妛, which found its corporeal counterpart in the 国土行政区画総覧 (Kokudo Gyōsei Kukaku Sōran, National Conspectus of Administrative Districts), 彁 was documented as “completely unique among the graphic characters encoded in these standards, with absolutely no means of identification.”
https://www.japantimes.co.jp/life/2018/10/29/language/ghost-kanji-lurk-japanese-lexicon/
