(Note) We cannot guarantee that the translation is complete.
September 16, 2025
When applying the chronology according to the imperial (Kōki) calendar, I found the following:
The year of Emperor Ankō’s death and Emperor Yūryaku’s accession is not 464, but 463.
The transition from the double-year calendar (bireki) occurred not in 471, but in 470, during the 14th year of Emperor Yūryaku.
Accordingly, I will make these corrections.
September 16, 2025
Revised to correct an error: Empress Jingū’s age at death was 100 years, not 101.
November 17, 2025
The year of Emperor Ingyō’s death is not 462, but 461.
From an analysis based on the Five Kings of Wa, it has become clear that the structure of the Nihon Shoki is as follows:
Until the 14th year of Emperor Yūryaku (corresponding to 470 AD), the records follow a doubled calendar system, counting one year per spring and autumn (i.e., “2-year calendar”).
From the 15th year of Emperor Yūryaku (471 AD), the calendar system reverts to the standard method of one year per year (i.e., end of the double-year system).
Until the 13th year of Emperor Yūryaku (corresponding to 469 AD), the records follow a doubled calendar system, counting one year per spring and autumn (i.e., “2-year calendar”).
From the 14th year of Emperor Yūryaku (470 AD), the calendar system reverts to the standard method of one year per year (i.e., end of the double-year system).
The reign periods of Empress Jingū and Emperor Ōjin are absorbed within the reign of Emperor Nintoku.
If we mechanically apply this structure to the Five Kings of Wa based on the above rules:
| Emperor Name | Reign Years in Nihon Shoki | Actual Years (if double calendar) | Assumed Accession Year | Assumed Death Year | Years in Chinese Records of the Five Kings |
|---|---|---|---|---|---|
| (Emperor Ōjin) | (41) | (20) | (391) | (411) | |
| Emperor Nintoku | 87 | 43 | (391) | 413–434 | San (讃): (413), 421, 425, (430) |
| Emperor Richū | 6 | 3 | 434 | 437 | |
| Emperor Hanzei | 5 | 2.5 | 438 | 440 | Chin (珍): 438 |
| Emperor Ingyō | 42 | 21 | 441 | 462 461 | Sai (済): 443, 451, (460) |
| Emperor Ankō | 3 | 1.5 | 462 | Kō (興): 462 | |
| Emperor Yūryaku | 23 | 7（+9） 6.5+10 | 479 | Bu (武): (477), 478, possibly 479 | |
| Emperor Seinei | 5 | – | 480 | 484 | |
| Emperor Kenzo | 3 | – | 485 | 487 | |
| Emperor Ninken | 10 | – | 488 | 498 | |
| Emperor Buretsu | 8 | – | 498 | 506 | |
| Emperor Keitai (Confirmed) | 25 | – | 507 | 531 |
About the Sword from the Inariyama Kofun
The iron sword unearthed from the Inariyama Kofun is known to be the oldest artifact discovered in Japan with a date inscribed using the ten heavenly stems and twelve earthly branches (Jikkan Jūnishi system), believed to most likely correspond to the year 471 (though some argue for 531).
However, I believe it is not just the oldest discovered artifact, but likely the actual oldest artifact bearing a specific year in Japan. In other words, and this is my personal opinion, I speculate that it was created as a commemoration of the calendar reform.
Records of Empress Jingū, Emperor Ōjin, and Emperor Nintoku
Given the alignment with the years of the Five Kings of Wa, the year 391—when Wa is said to have crossed over to the Korean Peninsula according to the inscription on the Gwanggaeto Stele—can be seen as the first year of Emperor Nintoku’s reign. This suggests that both the regency period of Empress Jingū and the reign of Emperor Ōjin are effectively absorbed into the years of Emperor Nintoku.
Considering the Nihon Shoki, the 41-year reign attributed to Emperor Ōjin likely corresponds to a period when Empress Jingū served as regent. The title “Taichū Tennō” (Emperor in the Womb) given to Ōjin implies that political power during this period was exercised by his mother, Empress Jingū.
The blank period between Ōjin’s death and Nintoku’s accession may reflect a mourning period following Empress Jingū’s death. It is reasonable to consider that Emperor Nintoku’s reign began with the end of mourning and his personal rule. Therefore, the 87-year reign attributed to Emperor Nintoku likely reflects his age at death, not his actual reign length (which would be 43 years).
(This suggests that Emperor Ōjin and Emperor Nintoku may have been either the same person or twin brothers.)
Why was the 69-year regency of Empress Jingū recorded?
Possibly because the period from Emperor Chūai’s death to the final records of Empress Jingū coincidentally adds up to 69 years. Including this span enabled a near match with the records in the Gishi Wajinden (Record of the Wa People in the Wei Chronicles). It may have been customary to include her records as she was known to have governed politically. (Kojiki has a similar structure.)
Moreover, the disappearance of records after 69 years could imply that, after Emperor Ōjin grew to around ten(five) years old, records began to be compiled under his name.
According to the Nihon Shoki, there is an entry in the 3rd year of Emperor Ōjin that records the transition of the Baekje kingship from King Jin-si (辰斯王) to King A-hwa (阿花王 / 阿莘王). This change in rulership is conventionally dated to the year 392 CE.
In addition, the entry for Empress Jingū’s 62nd year contains a record of a Japanese military expedition to Silla. The same entry cites a passage from the Baekje Annals (Baekje-gi), stating that this expedition occurred in a year designated “壬午 (Jin-wu)”, which follows the traditional sexagenary cycle used throughout East Asia.
Within the surrounding chronological range, 382 CE corresponds to a Jin-wu (壬午) year. Based on this, if Empress Jingū’s 62nd year is aligned with 382 CE, and Emperor Ōjin’s 3rd year is aligned with 392 CE, the two reigns can be made to connect continuously without contradiction. Therefore, it may be inferred that the compilers of the Nihon Shoki designated 69 years for Empress Jingū’s reign as a result of aligning these chronological data points.
— November 17, 2025
(Note:
The Baekje Annals cited in the entry for the 62nd year of Empress Jingū is most likely referring to the sexagenary year Rén-wǔ (壬午) of 562 CE.
See also:
“A Tentative Hypothesis on the Lineage of Emperor Nintoku,”
DOI: 10.5281/ZENODO.17221407
“『日本書紀』に見る4世紀末から5世紀後期の外交記録の一考察”
DOI: 10.5281/ZENODO.17474831 ）
When tracing back to the Yamatai period from 391…
It aligns with Emperor Kaika’s 51st or 52nd year through to Emperor Sujin’s 9th or 10th year (noting the double-year calendar, hence two options). The pestilence during Sujin’s reign, the subsequent religious rites by Toyosukiiri-hime (豊鍬入姫命), and her imperial status closely match descriptions in the Gishi Wajinden.
Since Chinese envoys likely received their information upon arriving at Itokoku (伊都国), some discrepancies are natural, but the core is probably accurate.
About Suishō, King of Wa (107 AD)
The envoy dispatched by King Suishō of Wa to the Later Han Dynasty in 107 AD corresponds—when viewed using the double-year system—to the reign of Emperor Kōan (孝安天皇). Given his name includes kunioshihito no Sumeramikoto, the correspondence seems highly probable.
When tracing back, omitting the years of Empress Jingū and Emperor Ōjin maintains consistency, suggesting that original records may have mistakenly listed Jingū, Ōjin, and Nintoku sequentially.
(Since the conquest of the Three Kingdoms is said to have occurred in Empress Jingū’s first year, events before 391 are unlikely and are thus excluded from the years of Jingū and Ōjin.)
Thus, the structure of the Nihon Shoki is as follows:
Until the 14th year of Emperor Yūryaku (470 AD), records follow a doubled calendar system.
From the 15th year of Emperor Yūryaku (471 AD), the system ends, and regular calendrical counting begins.
Until the 13th year of Emperor Yūryaku (469 AD), records follow a doubled calendar system.
From the 15th year of Emperor Yūryaku (470 AD), the system ends, and regular calendrical counting begins.
The reigns of Empress Jingū and Emperor Ōjin are absorbed within Emperor Nintoku’s reign.
Summary of the Most Likely Cause of Confusion in the Nihon Shoki: The Relationship between Empress Jingū, Emperor Ōjin, and Emperor Nintoku
| Name | Reign in Nihon Shoki | Assumed Reign Period | Actual Reign | Birth Year | Assumed Death Year |
|---|---|---|---|---|---|
| Empress Jingū | (Regency) 69 years | 41 years | 20 years | c. 361 or 362 | 411 |
| Emperor Ōjin | 41 years | 41 years | 20 years | 391 | 434 (or 411?) |
| Emperor Nintoku | 87 years | 46 years (87–41) | 20–23 years (43–20–3) | 391 | 434 |
*If Emperor Ōjin died in 411, then based on the reign years of Emperor Nintoku recorded in the Nihon Shoki, it implies that Emperor Ōjin and Emperor Nintoku were twin brothers.
(Or possibly the same individual. In that case:
The first half of his rule, as Emperor Ōjin, was under the regency of Empress Jingū
The latter half, as Emperor Nintoku, marked his personal reign.
This interpretation is more consistent, though no definitive evidence proves which is correct.)*
Alternative Names for Emperor Ōjin:
胎中天皇 (Taichū Tennō)
はらのうちにましますすめらみこと (Haranoutinimashimasu-sumeranomikoto)
“Emperor in the womb”
Possibly “under the protection of the mother”
Clarification of Empress Jingū’s “101 100Years of Age and 69 Years of Regency”
| Classification | Description | Interpretation | Cause | Analysis |
|---|---|---|---|---|
| Regency (69 years) | Actually about 34 years in real time (based on double calendar) | More likely a chronological record from birth, i.e., age record | The original record had “69 years of records” + a gap + “died at age 101,” and compilers misinterpreted the 69 years as the full regency | A structural error that mistook age records for political reign; not related to actual governance |
| Remaining 31 years Remaining 32 years | About 16 actual years | Transferred into the administrative records of Emperor Ōjin | Possibly because Emperor Ōjin was too young and the first 10 years were under the name of Empress Jingū | Emperor Ōjin was nominally enthroned → governance under Empress Jingū’s name → gradual transition to Emperor Ōjin’s official records |
| Mourning Period Gap | From Emperor Ōjin’s death to Emperor Nintoku’s accession | Possibly Emperor Nintoku (same as Ōjin) mourning his mother Empress Jingū’s passing | Reflected as a period of missing records | Offers a natural explanation for the delay in Emperor Nintoku’s official enthronement |
Foreign Affairs Articles in the Empress Jingū Section (Chronologically Disordered)
| Issues | Reasons |
|---|---|
| Resemblance to the Gishi Wajinden notes | If one mechanically traces dates back in the Nihon Shoki, it lands in the mid-3rd century, prompting forced insertions |
| Inconsistencies with Baekje king succession | Probably due to using the 52nd year of Empress Jingū as a baseline, regardless of historical accuracy |
| Issues in citation methods of source material | Likely due to not accounting for the doubled calendar; Baekje records may have been forcefully matched to Empress Jingū’s regnal years without proper adjustment |
| The Three Kingdoms Conquest (Sankan Seibatsu) | Since the records mention this event right after Emperor Chūai’s death, it was mechanically assigned to Empress Jingū’s first year |
It appears that the Nihon Shoki calculates the age of emperors primarily based on their reign years.
Thus, when unusual circumstances occur in the imperial line, the reliability of recorded ages seems to decrease.
This applies particularly to the period after Emperor Chūai, involving Empress Jingū, Emperor Ōjin, and Emperor Nintoku.
Likewise, in the case of Emperor Keitai, it seems the age at death of Emperor Buretsu was included in the account for Emperor Keitai, and they simply added the reign years from the time of Buretsu’s death.
Therefore, the Kojiki’s record of Emperor Keitai dying at the age of 43 might be more accurate.
Even if we consider them the same person, the fact that Emperor Keitai is described as a fifth-generation descendant of Emperor Ōjin could be interpreted as referring to the lineage under the name of Emperor Ōjin. This may not necessarily be a contradiction.
Fundamental Misunderstandings in Modern Research on the Nihon Shoki and the Need for Reassessment
1. Misinterpretation of Chronological Structure
It is widely held that the Nihon Shoki does not provide an accurate account of historical facts, but rather represents a post-facto narrative blending mythology and later political motives. The reliability of its year-by-year records is particularly questioned.
Nevertheless, many studies continue to use the Nihon Shoki as a primary source for chronological analysis, resulting in a contradictory double standard.
2. Prevalence of Arbitrary Interpretations
As a result, in the field of ancient Japanese history, it has become common practice to selectively cite only the passages from the Nihon Shoki that appear to support one’s own theory, and to repeatedly engage in “interpretation for the sake of interpretation” by arbitrarily aligning elements such as the sexagenary cycle, astronomical phenomena, traditions, and mythological motifs.
This fundamentally stems from a failure to recognize structural misinterpretations—such as double dating (bai-reki) or the recording formats—which has led to a misunderstanding of chronological discrepancies in the Nihon Shoki.
3. Effects of Editorial Distortions
In particular, with regard to the relationship between Empress Jingū, Emperor Ōjin, and Emperor Nintoku, the treatment of these figures as historically independent entities in the records contains a critical structural flaw in the Nihon Shoki‘s historiography. It is highly likely that the chronological consistency had already collapsed at the time of the compilation.
By artificially dividing what should have originally converged around the life of Emperor Nintoku into fictitious generational segments, subsequent research has been conducted on a distorted timeline.
Since diplomatic records appear to have been constructed by using the chronological entries in Japanese sources as the reference point, and then fitting foreign historical texts—such as the Gishi Wajinden and the Baekje Bonki—to those dates, it is likely that many accounts involving foreign countries exist within a distorted temporal framework.
4. Academic Consequences
All subsequent works annotated or edited on the basis of the Nihon Shoki—including early commentaries, critical editions, academic studies, and textbooks—are thought to be based on a fundamentally flawed chronological premise, and have likely unintentionally contributed to historical misconceptions.
Unless this structural misreading is corrected, it seems to me that research on ancient Japanese history will continue on an unstable foundation.
5. What Must Be Done
Rather than focusing on the fictitious nature of the Nihon Shoki, reexamining its structural features that have been misread may make it possible to restore its chronological records to a level where they can be used as historical sources.
Therefore, it seems that all historical annotations and widely accepted interpretations related to the Nihon Shoki should be open to reconsideration and possible revision. Accordingly, it appears that historical research based on documentary sources concerning Japan prior to the 5th century will also need to be reexamined.
In foreign records, it seems necessary to first set aside any entries that are not based on what appear to be original Japanese sources, and then reassign them to more appropriate points in time.