Kyōka Suigetsu

Kyōka Suigetsu looks like an unremarkable katana. It carries a metallic-gold guard cut into a hexagon, a hilt bound in green wrapping that leaves the usual diamond gaps, and a golden pommel, all sheathed in a green scabbard that the anime renders black. The blade shows no outward change between its sealed state and its released Shikai.

The Shikai answers to the command Shatter, a word that both switches the ability on and turns it off. Its power, Kanzen Saimin, or Complete Hypnosis, seizes control of all five senses, so Aizen can make a target misjudge the form, shape, mass, texture, and even smell of anything, turning a fly into a dragon or a swamp into a flowering garden in the victim's eyes. The trap has a single trigger: anyone who watches the Shikai released even once falls permanently under its sway, succumbing again with every future release no matter how much time has passed. The blind, unable to see the release, stay immune. For years the Gotei 13 believed the blade was merely a water-type weapon that scattered reflections through fog and water to turn foes against each other, exactly the cover story Aizen fed them. Its lone flaw is subtle: the sword's own Reiatsu, distinct from Aizen's, can betray its presence to a hypnotized victim in direct contact with the weapon, above all when the blade pierces the body.

Aizen wielded the blade to deceive nearly all of Soul Society for more than a hundred years, keeping its true ability secret while advancing his schemes. During the invasion of the fake Karakura Town he traded places with Momo Hinamori through illusion and cut down a string of captains who could not tell where he truly stood. His long con finally cracked when Gin Ichimaru, exploiting the weapon's hidden weakness, turned on him. Later, in the war against Yhwach, Aizen used Kyōka Suigetsu to warp the emperor's sense of time, only to find that Ichigo Kurosaki, who had never once seen the Shikai released, lay wholly beyond its reach, a gap Aizen came to treat as the final piece of his plan. The name itself, a four-character idiom, hints at its nature: a flower in a mirror and the moon on water can be seen but never held, images with no substance behind them. In reader polls the sword placed eighteenth in the first Zanpakutō ranking and seventh in the second.