Kira Yoshinaka, born in 1641, was the eldest son of Kira Yoshifuyu.
His mother was a member of the high-ranking Sakai clan.
On the death of his father in 1668, Yoshinaka had become the seventeenth head of the household, inheriting lands valued at forty-two hundred koku.
His wife was from the Uesugi clan, and his eldest son has been adopted by Uesugi Tsunakatsu, the head of the Dewa Yonezawa han, taking the name Tsunanori.
Yoshinaka had named his second son as his heir, but when that heir died, Yoshinaka had adopted Tsunanori's second son, strengthening the connection between the Kira and the Uesugi.
Asano Naganori was born in Edo as the eldest son of Asano Nagatomo.
His family is a branch of the Asano family, whose main lineage is in Hiroshima.
His grandfather Naganao had been appointed to the position of daimyo of Ako with 50 thousand koku.
After Naganao died in 1671, Nagatomo had succeeded to the position but died after three years in 1675.
Naganori had succeeded his father at the age of nine.
He had in 1680 been appointed to the office of Takumi no Kami, the head of carpentry at the imperial court, but this office was nominal, as were other offices granted to samurai at that time, and only had an honorific meaning.
As a daimyo with a small fief, he had been appointed several times to temporary minor offices of the Tokugawa shogunate.
He had first been appointed in 1683 to be one of two officials to host the emissaries from the imperial court to the Shogunate.
It was the first time he met Kira Yoshinaka, the highest-ranking koke, the head of ceremonial matters at the Shogunate, who instructed officials in the manner of hosting noble guests from Kyoto.
He had suffered in 1694, from a serious illness.
He had no children, thus no heir at that time.
When a daimyo dies without a determined heir, his house is abolished by the Shogunate, and his lands confiscated; his retainers become ronin.
To prevent this, he has adopted his younger brother Asano Nagahiro, titled Daigaku, and Nagahiro had been accepted as his heir by the Shogunate.
He is in 1701 appointed for the second time to the same office.
It is said that he was at this time on bad terms with Kira Yoshinaka and tension between them increases.
Kira has been assigned the task of tutoring Asano in matters of protocol in preparation for an upcoming visit by representatives of the Emperor.
According to the stories, Kira was corrupt and demanded bribes for the tutoring, which Asano refused to pay.
Kira then began to publicly insult Asano, calling him an ignorant and unmannered rural boor.
On April 21, the day when the envoys are scheduled to meet the fifth Tokugawa shogun, Tsunayoshi, at Edo Castle in what is now Tokyo, Asano draws his short sword and attempts to kill Kira in the Corridor of the Pines.
He wounds Lira but fails to kill him.
Tsunayoshi on the same day, sentences him to commit seppuku, which he does after writing his death poem.
He is buried in the graveyard of Sengaku-ji.
His retainers become ronin when the Shogunate confiscate his fief.
A group of forty-seven former samurai in his service, now with the status of ronin, begin planning to avenge their master’s death.
