By noon of March 14, 1701, Edo was abuzz with rumors about what had happened earlier, in the "Great Pine Corridor" of the shogun's castle. Officials posted wooden signs around the city stating that Asano Naganori, lord of Ako Domain, had attacked and wounded his former tutor, Kira Yoshihisa.

A number of explanations have been suggested for the attack, but exactly why Asano unsheathed his sword on that fateful day in Edo (now modern-day Tokyo) remains a mystery. Inspector Okado Denpachiro, who interrogated both parties after the incident, said that Asano admitted to holding a grudge against Kira and that Asano's only regret had been his failure to kill the man.

To draw a weapon within the castle was a great breach of etiquette and Asano was sentenced to death by his own hand the same day.