Ren

Ren (練, Ren) is one of the four basic Four Major Principles of the Shingen-Ryu school of Kung-fu Nen techniques.

Description
Ren (練, Refine; Enhance) is a direct application of Ten. Since a user is capable of keeping aura from leaking away from the body, it's also possible for them to produce more aura around themselves without having to worry about losing it. Ren focuses on outputting a high amount of aura and keeping it on the body, expanding the size and intensity of it. If Ten is considered to be purely defensive, then Ren typically what is used for offense. This increases the user's physical strength and durability and provides a large pool of aura for any advanced techniques or individual skills they decide to use.