However, when Kira Kozuke no Suke and a bakufu hatamoto (direct retainer of the bakufu) Yoriteru KAJIKAWA were discussing the ceremony at the Great Pine Corridor in Honmaru Palace of Edo-jo Castle at around 10 a.m., Asano Takumi no Kami suddenly attacked Kira Kozuke no Suke with a small sword.
しかし同日巳の刻（午前10時ごろ）、江戸城本丸御殿松之大廊下（現在の皇居東御苑）において吉良上野介と旗本梶川頼照が儀式の打合せをしていたところへ、突然、浅野内匠頭が吉良上野介に対して脇差による殿中刃傷に及んだ。