Jiko Hakai Katana

The Jiko Hakai Katana is Gustav's signature physical weapon through the middle and later story. It releases enormous lightning-wreathed destructive arcs, but its output is reflected onto the wielder and can maim or kill someone who exceeds their safe limit.

History

Selection from the MBO stores

Gustav sees the red-hilted katana while drawing equipment for a mission and chooses it despite Officer Milly's warning that it is too powerful for him. Contact immediately burns and electrocutes his hand. When he unsheathes and swings it, the four-foot red blade releases a twenty-seven-foot arc that cleaves and ignites roughly seventy trees. His durability, pain tolerance, and regeneration let him remain conscious where many officers would collapse. (Chapters 519–520)

The System explains that greater destruction causes greater backlash: full output at Gustav's then-current condition would remove his arm, while combining maximal transformations and boosts could destroy half his body. The weapon belongs to the MBO stores when selected, but Gustav later decides not to return it and keeps it among his mission equipment. The story establishes possession and continuing custody, not a formal transfer of legal ownership. (Chapters 520, 589)

A weapon worth losing an arm for

Gustav first uses the katana decisively against Zergeref, sending an eighty-nine-foot arc through the enemy's attack and body. He later undergoes specialized instruction to raise the input without suffering the worst backlash. Learning the technique costs him an arm several times during practice, but regeneration makes the training survivable. The improved control turns the sword from a desperate finisher into a weapon he can integrate with movement, barriers, and other abilities. (Chapters 566, 825)

The katana remains dangerous to other wielders. Stark seizes it during an emergency and cuts the Beta-ranked dragon master, but both of his arms explode from the backlash. Gustav subsequently uses the weapon against the Gisodinym, driving it through the creature's head and channeling destructive energy internally, and later cuts through battlefield domains and cosmic opponents. Its latest shown uses still depend on Gustav's exceptional body and practiced control rather than any removal of the underlying cost. (Chapters 914, 1012–1014, 1302–1305, 1393)

Abilities and properties

• Produces red destructive slashes threaded with blue electricity; output can travel far beyond the physical blade and cut through attacks, structures, and large bodies. (Chapters 520, 566)
• Scales with the power placed into a swing, but the wielder receives correspondingly severe electrical and physical backlash. (Chapter 520)
• Can destroy an arm or more of the wielder at high input; Gustav mitigates rather than abolishes this risk through specialized training and regeneration. (Chapters 520, 825)
• Can channel destructive energy after penetration, allowing Gustav to kill the Gisodinym from inside its skull. (Chapter 1014)
• Is usable by another person, but Stark's emergency swing demonstrates that recognition or possession does not grant safe handling. (Chapter 914)

Ownership and custody