Zetsubou No Shima:
KT-4 and Masamune

The KT-4 of Zetsubou No Shima: what its green liquid does to zombies, Thrashers, spiders and plants, its three ingredients, the vial, the venom and the plant, and the Masamune upgrade with the Liquid Divinium, the spider fang and the rainbow water.

3 min read
4 chapters
updated 2026-10-18

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The KT-4

The KT-4, short for Kusanagi-no-Tsurugi, is the wonder weapon of Zetsubou No Shima. It sprays a green liquid that grows spore bags on zombies until they burst. A shot can be charged up to three times, and a full charge leaves a bubbling pool on the ground that hurts every zombie walking through it. A melee cancels the charge.

Against Thrashers

It breaks their spores, and a full charge can kill one outright after a few seconds.

Against spiders

It bursts the small spiders at once, and clears the webs on paths and machines.

On plants

A shot on a watered Seed fertilises it and raises the chance of a rare plant.

On wall spores

It turns their orange cloud blue. A blue cloud stops the coughing and gives more speed and a longer sprint for a while.

Building the KT-4

The KT-4 already waits on its bench in the operations room of the Bunker, but it needs an ammunition made from three ingredients.

The vial

A scientist zombie glowing yellow-green carries it on his hip. He only appears once the main power is on, most often around Lab B, and drops the vial when killed.

The jar of spider venom, KT-4 ingredient icon, Zetsubou No Shima, Call of Duty Black Ops III Zombies

The spider venom

In Lab A, the control panel lowers a cage into the swamp. A spider lured close enough walks into it. Raising the cage back up makes a syringe draw its venom and kills it. If it was the last spider of a spider round, the Max Ammo appears in the cage.

The plant

At the very end of a tunnel of raw Element 115, in the flooded caves past Mule Kick. Air pockets and spores help to get there and back.

With the three ingredients, the bench gives the KT-4. Every player can then take one, and the KT-4 starts to appear in the Mystery Box.

The Masamune

The KT-4 cannot be Pack-a-Punched. It is upgraded into the Masamune with a stronger ammunition, made on the second bench, against the back wall next to the first one. The Masamune is needed for the final step of the Easter egg. None of its three ingredients shows a pickup prompt, only a line from the character.

The vial of Liquid Divinium

With a Zombie Shield electrified by the lightning of the ritual altar, a melee on the control panel of Lab B opens its cage. The cage goes down under the lab, where a skeleton holds the vial in its ribs. In co-op, another player works the panel.

The spider fang

Pulled from the body of the Giant Spider, in the cave behind the blue water near Lab A.

The special plant

The Skull of Nan Sapwe first reveals a torn blueprint in the Living Quarters, then a hidden planter in the wall to the right of where the first plant was found. A Seed planted there must be watered for three rounds with the rainbow water of the Sewer Pipe.

The rainbow water is caught inside the Sewer Pipe, from a small lump of Element 115 on the right side of the pipe. The most consistent way is to ride the pipe from the Bunker towards Lab B and press the use button just after the second blue section. Each ride costs 500 points. The second bench only answers when the KT-4 is in hand.

	KT-4	Masamune
Magazine	6	6
Reserve	36	36
Fire	Semi-automatic, charged shots	Semi-automatic, charged shots
Chain effect	Standard	5 seconds longer

In the First Room

Neither weapon can be had doors closed: the bench and the plant are in the Bunker, the vial and the venom need the main power, and the Box has no spot in the spawn area.