Tetsuigan

Background
The Tetsuigan is a signature Kekkei Genkai based dōjutsu of the Ekazu clan. Created by Denkaichi fifteen hundred years ago, the Tetsuigan has an incredible ability. A Tetsuigan user's strength is greatly enhanced, along with increased speed and reflexes. The user's reflexes are refined to a point where they're granted a faint, cognitive vision that allows them to foresee their opponent's moves should they remain in their line of sight. The increased abilities is caused by the Tetsuigan's energies opening the body's ability to produce bloodflow into the extremities, allowing them to move faster, strike harder and react more efficiently. This is why exhaustion sets in after it is over. Such an increase in bloodflow, followed by a drastic drop to normal levels causes the body to go into a sort of emergency, energy rationing state.

Attaining the Tetsuigan
Once every five hundred years, a member of the Ekazu is granted this ability. It's with them after birth, but doesn't begin to take form until the user achieves a peak, physical form and keeps a strong concentration on their physical energy. Once awakened, all the user needs to do is keep their concentration on their physical energy strong just long enough for the Tetsuigan to fully take hold.

Perfect State
After constant training with the base Tetsuigan, one can bring it up to the next level, known as the Perfect Tetsuigan (完全 鉄眼). In this state, the user's physical strength is enhanced even further, giving them more power and speed. Among this is an even more boosted reflex time, further increasing the user's cognitive abilities. To achieve this state, one must concentrate on their physical energies, but at an even more tremendous rate. It would require at least three quarters of the user's physical energies to use properly, and leaves the user emanciated and exhausted after its use. The drawbacks are not as severe for a user of the perfect Tetsuigan. Should they fail to harness enough energy for the perfect state, but harnessed enough energy for the base Tetsuigan, they'll go into that form, instead.

Drawbacks
Using the Tetsuigan puts a tremendous strain on the body and requires peak, physical condition to use properly. One must also be fully concentrated on his or her physical energy in order to grab hold of the energy brought forth from the Tetsuigan. If they can't keep concentrated long enough for the Tetsuigan to fully go into effect, their bloodflow levels drop drastically and can be fatal if too much blood to the brain is lost.