Sensui Kanzaki, a samurai exiled from the early Edo period, bears the epithet “Senningiri” (Thousand Men Slasher) for his ruthless efficiency in slaughtering foes during the Sengoku era. Wielding dual blades—Suigetsumaru, a Japanese katana, and Halbert, a Western sword—he inherits both weapons from his adoptive father, a foreign swordsman, and Jouzen Matsumoto, his later master who oversaw the Nen-ryuu dojo. After accepting blame for Matsumoto’s failures at the Battle of Sekigahara, Sensui is cast into exile, journeying alongside ninja Kenroku Sanada until a violent storm strands them in 2030’s apocalyptic Tokyo.

There, he faces a desolate world overrun by the Gibia virus, a pathogen mutating humans into grotesque monsters. Haunted by his blood-soaked past, Sensui swears a vow against killing, relying on defensive tactics—until grim necessity forces him to mercy-kill infected allies. He grants Maeda’s plea for death before transformation and decapitates Ayame Hatonami to spare her father anguish. His unmatched swordsmanship carves through Gibia hordes, drawing admiration from survivors like Kathleen Funada, a scientist battling the outbreak.

A survivor of his clan’s annihilation, Sensui was adopted by Halbert and molded into a warrior. Loyalty to Matsumoto and guilt over his master’s execution haunt him, compounded by discovering Matsumoto’s future betrayal and beheading. When rage consumes him, his eyes blaze crimson, reflecting his battle to suppress violent instincts.

In the ruined future, he allies with warrior monk Yukinojyo Onikura and clashes with outlaw factions like Renjiro Hatonami’s Galients. Ultimately, infected by Gibia, Sensui embraces self-sacrifice, remaining behind to hold off endless monsters—a final act upholding his oath to shield others, even as his own fate dissolves into the chaos.