The Lords of the Akō Domain in Harima Province associated with the story of what 18th-century historical event in Japan in which a band of "rōnin" (leaderless samurai) avenged the death of their master?
Asano clan:  The Main Lineage ("sōke", 宗家) were Lords (daimyō) of the Hiroshima Domain in Aki Province and another famous branch family were Lords of the Akō Domain in Harima Province associated with the story of the Forty-seven rōnin. Forty-seven rōnin: The revenge of the forty-seven "rōnin" (四十七士 , Yon-jū-shichi-shi , forty-seven samurai) , also known as the Akō incident (赤穂事件 , Akō jiken ) or "Akō vendetta", is an 18th-century historical event in Japan in which a band of "rōnin" (leaderless samurai) avenged the death of their master.
forty-seven "rōnin"