Irooni

is a technique of Shunsui Kyōraku's Zanpakutō, Katen Kyōkotsu.

Description
This is a color-based game where the participants say the name of the color they want to cut with their weapons and are unable to cut anything else. If the color the participant calls does not exist on their body, the damage is minimal, even if the attack would normally inflict a much more severe wound. The opposite is true as well; by calling out a color they are wearing and attacking, the damage dealt is proportional to the amount of that color on them. To maximize damage, the participants have to use a color which maximizes the risks to themselves, as well as their enemy's. For example, by wearing black robes and naming black, one would inflict massive damage on an enemy if they hit, even if the actual blow itself was minimal or minor, but the caller would also suffer severe damage if they are struck by the enemy in return.