However, around 11 a.m. just before the ceremony, Naganori approached Yoshinaka KIRA from behind while Kira was having a meeting about the ceremony with hatamoto (bannermen) Yoriteru KAJIKAWA at the Great Corridor of the main ward of Edo-jo castle (common name; matsu no roka [literally, a corridor of pine trees]), and Naganori slashed Kira with a short sword.
ところが、儀式直前の巳の下刻（午前11時頃）、江戸城本丸大廊下（通称松の廊下）にて、吉良義央が旗本梶川頼照と儀式の打ち合わせをしていたところへ、長矩が背後から近づいてきて、突然吉良義央に対して脇差でもって刃傷に及ぶ。