second accession of the same emperor
Historical term referring to the second enthronement ceremony of an emperor who had previously abdicated and then re-ascended the throne. Rare and domain-specific to Japanese imperial history.
Kōi is a ceremony performed when an emperor who once abdicated ascends the throne again.
Compound of 更 (kō, 'again; renew') and 位 (i, 'rank; throne'). The exact historical derivation is uncertain, but the term is conventionally associated with the concept of re-ascending the imperial throne.