Aera

 (勢力), also known as Ki (気), is the life-force energy used by living beings in Endless Utopia Online.

Overview
Seiryoku is also known as "latent energy" or "fighting power." Which directly translates as "life force." This force is a tangible energy inside every living being, with its major focus being in the center of the body. By drawing it out, an individual is able to manipulate it and use it outside the body, and so, be used for techniques.

Seiryoku Control
This energy is not limitless, since all players have a max capacity of Seiryoku that they can form and use before it runs out and they need to rest to replenish it. With practice, the quantity can be extended.