The diplozoid monogenean Eudiplozoon nipponicum (Goto, 1891) is a gill parasite of crucian carps (Carassius spp.) and common carp (Cyprinus carpio) in Japan. This note compiles information on the host species, geographical distribution, life history, maturation and spawning, occurrence related to fish size, pathogenicity, and control of the species based on the literature published in Japan for 126 years from 1891 and 2016. Since the 1970’s , an unidentified diplozoid has been reported as Diplozoon sp. from various cyprinids in Japan. This diplozoid is very likely to be Paradilpozoon skrjabini Akhmerov, 1974, another species of diplozoid reported from Japan in 2015. The titles of scientific papers, a book, and oral presentations at academic meetings by Dr. Satoru Kamegai on the biology of diplozoids are listed in the appendix.