Lord Mifune was Usagi's Lord until his death in the Battle of Adachigahara Plain. Lord Mifune was a man of mercy and honor such as when he was presented with a young Usagi, wrongly accused of looting the war dead. Mifune believed the child's firm honest denial of the charge and allowed him to leave unharmed. He later saw Usagi as a young adult winning at a tournament, bestowed a daisho as a prize and hired the rabbit as a retainer. When Mifune's family was assassinated by ninja sent on Lord Hikiji's orders, he made war and was only defeated when a subordinate commander defected from him to Hikiji. However, even death could not silence his spirit completely such as what happened to Usagi after the samurai fled the lost battle with his lord's head and buried it in secret to prevent it from being desecrated. After that act of honor, Usagi fell into the clutches of a supernatural entity and was saved only when the spirit of Mifune appeared and slew the entity for his loyal retainer.
Lord Mifune was named after famed Japanese actor Toshiro Mifune.