Fortify

(堅, Fortify) is the advanced version of the basic Ren and Ten techniques. It is a primarily defensive technique where a Nen user maintains a state of Ren for a prolonged amount of time. The amount of aura surrounding the user's body during Ken is about 10 times higher than during Ten. Ken allows a Nen user to guard against attacks from any direction, but the large amount of aura produced makes it tiring to maintain. It is considered the best option to defend from Ko, despite not being as powerful as the latter on any given part of the body, as it protects all of it evenly. When not immediately at risk of being struck with Ko, Ken is utilized when one wants to be cautious. Some Nen users choose to expand its radius so as to sense incoming attacks they are unable to see, as a miniature En of sorts. Sometimes Ken is colloquially called Ren owing to the similarities between the two techniques.

See Also: Iron Body