, also known as in the , and or in the was the tenth Emperor of Japan. While Sujin is the first emperor whose existence historians widely accept, he is still referred to as a "legendary emperor" due to a lack of information available and because dates for his reign vary. Both the , and the (collectively known as the Kiki) record events that took place during Sujin's alleged lifetime. This legendary narrative tells how he set up a new shrine outside of the Imperial palace to enshrine Amaterasu. He is also credited with initiating the worship of Ōmononushi (equated with the deity of Mount Miwa), and expanding his empire by sending generals to four regions of Japan in what became known as the legend of Shidō shogun.
This Emperor's reign is conventionally assigned the years of 97 BC – 30 BC. During his alleged lifetime, he fathered twelve children with a chief wife (empress) and two consorts. Sujin chose his future heir based on dreams two of his sons had; in this case, his younger son became Emperor Suinin upon Sujin's death in 30 BC. Like other emperors of this period, the location of Sujin's grave if it exists is unknown. He is traditionally venerated at the Andonyama kofun in Tenri, Nara.
Legendary narrative
The Japanese have traditionally accepted this sovereign's historical existence, and a kofun (tumulus) for Sujin is currently maintained. There remains no conclusive evidence though that supports this historical figure actually reigning. The following information available is taken from the pseudo-historical and , which are collectively known as or Japanese chronicles. These chronicles include legends and myths, as well as potential historical facts that have since been exaggerated and/or distorted over time. The records state that Sujin was born sometime in 148 BC, and was the second son of Emperor Kaika. The former name is used in the , while the latter two are found in the . Sujin was enthroned sometime in 97 BC, and during the 3rd year of his reign it is the recorded that he moved the capital to , naming it the Palace of Mizu-gaki or . Yamato-no-Okunitama (the other god) was entrusted to another daughter named , but her health began to fail shortly afterward. It is recorded that Nunakiiri-hime became emaciated after losing all of her hair, which rendered her unable to perform her duties.
Four Cardinal Quarters (Shidō shogun)
thumb|180px|The Four Cardinal Quarters
In his 10th year of rule, Sujin instituted four of his Generals to the Four Cardinal Quarters in what would be known as the Shidō shogun. These areas (west, north/northwest, northeast, and east) were all centered around the capital in Yamato Province. Sujin instructed his generals (shogun) to quell those who would not submit to their rule. One of the four shoguns who had been sent to the northern region was named , who was also Emperor Kōgen's first son. One day a certain maiden approached Ōhiko and sang him a cryptic song, only to disappear afterwards. Sujin's aunt , who was skilled at clairvoyance, interpreted this to mean that Take-hani-yasu-hiko (Ōhiko's half brother) was plotting an insurrection. Yamatototohimomoso-hime pieced it together from overhearing news that Take-hani-yasu-hiko's wife (Ata-bime) came to , and took a clump of earth in the corner of her neckerchief.
Emperor Sujin gathered his generals in a meeting upon hearing the news, but the couple had already mustered troops to the west who were ready to attack the capital. The Emperor responded by sending an army under the command of general Isaseri-hiko no Mikoto to fight a battle that ended with a decisive Imperial victory. Ata-bime was killed in combat, and her husband fled back north. In his 12th year of rule, the Emperor decreed that a census be taken of the populace "with grades of seniority, and the order of forced labour". The tax system meanwhile was set up so taxes imposed were in the form of mandatory labor. These taxes were known as for men and for women. During this period peace and prosperity ensued, and the Emperor received the title .
Choosing an heir and Divine treasures
During the 48th year of Sujin's reign (50 BC), he summoned two of his sons saying that he loved them equally and could not make up his mind which to make his heir. He then asked his sons to describe the dreams they had recently, so he could divine their lot by interpreting them. The elder son's name was , and explained to his father that he dreamt of climbing Mt. Mimoro (Mount Miwa). While facing east, he said that he thrust his spear eight times and then waved his sword eight times skywards. The younger prince, whose name was dreamt of climbing Mimoro and spanning ropes on four sides. He went on to say how he chased the sparrows that ate the millet. Sujin is also credited with building which was said to be located in Karu (Kashihara, Nara). Sujin's possible lifespan has been suggested to be as early as the 1st century AD, to as late as the fourth century AD, this is well past his conventionally assigned reign of 97 BC – 30 BC. Like Emperor Kōshō, Emperor Kōrei, and Emperor Kaika, historian Louis Frédéric notes an idea in his book Japan Encyclopedia that Sujin could have lived in the 1st century (AD). This remains disputed though, especially among researchers who have been critical of his book. If Sujin did in fact exist, then he may have been the founder of the imperial dynasty. Historian Richard Ponsonby-Fane suggests that Sujin may have been the first emperor to perform a census and establish and regularize a system of taxation. His name might have been regularized centuries after the lifetime ascribed to Sujin, possibly during the time in which legends about the origins of the imperial dynasty were compiled as the chronicles known today as the . While the actual site of Sujin's grave is not known, the Emperor is traditionally venerated at the Andonyama kofun in Tenri, Nara. The Imperial Household Agency designates this location as the kofun (tumulus), and its formal name is 'Yamanobe no michi no Magari no oka no e no misasagi.
Outside of the , the reign of Emperor Kinmei ( – 571 AD) is the first for which contemporary historiography is able to assign verifiable dates. The conventionally accepted names and dates of the early Emperors were not confirmed as "traditional" though, until the reign of Emperor Kanmu between 737 and 806 AD.