The Imperial Household Agency (Kunaichō 宮内庁) has a special department to handle written works about the Imperial Family and manage imperial mausoleums known as the shoryōbu (書陵部; literally, the “Department of Letters and Tombs”). They are responsible for compiling the official list designating which emperors are entombed in which kofun. Archaeologists sometimes find evidence that disagrees with the official designation, however.
Case in point: Nishitonozuka Kofun (西殿塚古墳; 234 meters; posited by some as the tomb of Himiko’s successor, Iyo/Toyo) is officially designated as the tomb of Tashiraka no Himemiko (手白香皇女). The problem with this designation is that Tashiraka no Himemiko, the legitimate wife of Emperor Keitai (継体天皇; 26th emperor) belongs to the 6th century. Nishitonozuka Kofun, however, is dated to the late 3rd century. This designation, therefore, does not hold water (page 98 of Adachi Noriyuki’s Gekihen! Nihon Kodaishi: Himiko kara Heijōkyō made [2010]).
There are two status designations of interest defined by the Imperial Household Agency: Ryōbo and Ryōbosankōchi.
Ryōbo (陵墓) are those tombs established by the agency as imperial mausoleum.
Ryōbosankōchi (陵墓参考地), on the other hand, refer to burial mounds in which the interred cannot be unequivocally determined, but have a high likelihood of belonging to the Imperial Family.
