TED-Ed Lesson: Asano Naganori, lord of Akō domain, fixed his gaze on Kira Yoshinaka, a senior master of ceremony. Asano extended his short sword, charged through the castle, and struck Kira. While the wound wasn’t fatal, its consequences would be. What brought about this violent quarrel? And what would come of Asano and his samurai? Adam Clulow shares the legend of the 47 Rōnin and their quest for revenge.