This paper is based on the author’s previous study “Observations on the Nihon Shoki from the Perspective of the Spring–Autumn Double-Year Calendar System” (DOI: 10.5281/zenodo.15306170). It presents a hypothesis concerning the reign and lineage of Emperor Nintoku, and also includes related considerations regarding the reign years of Emperor Keitai, under whom the imperial line shifted from that of Emperor Nintoku to that of Emperor Ōjin. Revision History Change Log (October 1, 2025) ・Revised the text two paragraphs before the conclusion of this section. ・Added a note before the “Additional note (from Previous Work ②)”. Change Log (January 26, 2026) ・Revised the note for 411CE in the section "1.Overlapping Accessions". Change Log (March 9, 2026) ・Expanded and revised Note 1 at the end of the section "1. On the Year Entries for Empress Jingū and Emperor Ōjin". Author's Note:This paper is licensed under CC BY-NC-SA 4.0. (Uses outside the following conditions—such as for commercial purposes or without the ShareAlike provision—require prior permission.) ・Attribution (BY): The author's name must be credited.・NonCommercial (NC): Free for non-commercial use, including summaries and translations. Commercial use requires prior permission.・ShareAlike (SA): Any derivative works (including summaries, adaptations, etc.) must be released under the same license (CC BY-NC-SA 4.0). Contact:For inquiries regarding this work (including permissions for commercial use), please visit the following website:https://tsurezureblog.sakuraweb.com/contact E-mail :h.shiina.contact@gmail.com
Hironobu Shiina (2026) studied this question.