Following the conclusion of the greatest father-son fight on earth, Baki and other legendary fighters are overcome with unbearable boredom. Meanwhile, 364 meters beneath Tokyo Skytree, a secret plan is set into motion that seeks to revive the master swordsman Miyamoto Musashi... Unleashed in the present day, this menacing new threat wields his swordsmanship with unparalleled power and speed to attack Baki and the others. It's the strongest underground arena fighters vs. the legendary swordsman! What will be the outcome of this mixed martial arts battle that crosses time and space?