東方の国の格闘用武器の一種。 圏とは金属製の輪の事であり、元々は舞踏用の道具であった。直径30cm弱程度の圏の外縁部に鋭い刃を付けたものを乾坤圏といい、円弧の一部を片手で握り、殴打して用いる。投擲武器として扱う事も可能で、東方の神が持つ乾坤圏は無限の射程を持ち、手元に戻ってくるという。
A type of fighting weapon from the East. A KEN is a metal ring, originally a tool used in dancing.A ken with a sharp blade attached to its outer edge is called a KENKONKEN, and a portion of the arc is held in one hand and used to strike an opponent.It can also be used as a throwing weapon, and the KENKONKEN held by the gods of the East is said to have an infinite range and to return to one's hand.