Maito Gai was from Kakashi's generation and was a talent in taijutsu, as was his father Maito Daí.
Maito Gai was a person for whom I had controversial feelings. If on the one hand I admired his tenacity and perseverance in his quest for power, on the other I despised his overly optimistic personal conduct. See, he was strong, but he didn't use his strength wisely. Let's look at his abilities in more depth.
There weren't many details about the creator of the eight inner gates technique, but if we were to use the deductive skills commonly associated with my genius intellect, it wouldn't be a mistake to assume Tobirama was to blame. Interestingly, he was not known for his talent in taijutsu, which leads me to believe that the technique was only theoretical and had never been tested before. It also proves that Tobirama's intelligence and genius had limits that his body could not think to overcome. Another example of a theoretical technique he created was the famous impure world reincarnation jutsu, which he historically never used and was only actually tested and completed by Orochimaru years after his death. The logic behind the eight gates technique was quite simple.
The eight gates technique consisted of the forced opening of specific points on the body that served to self-preserve the individual. These points were natural limiters that the technique basically crushed to create a temporary burst of energy dependent on body strength and amount of chakra. Just as we have some muscle strength controls that keep us from biting our tongue with all our strength, the Eight Gates regulate the flow of chakra in the individual's body. It is a natural protection for the body, protecting the user from getting hurt due to some kind of overexertion. But this also limits the user to using only 20% of the body's physical potential. To top it off, with each new gate there was an increase in pressure that broke the body little by little, while at the same time enhancing and multiplying the body's potential. If opening one or two gates an individual can use 100% of the body's occult potential, opening more digs potential from the depths of the anus (considering the screams Gai gave... kind of reminded me of someone defecating after eating spicy food, so the metaphor) to multiply that 100% by 10 or more times.
To train in the eight gates technique it was necessary to train the body extensively until it is able to withstand the explosion of chakra in these natural barriers to temporarily increase the basic status of the individual. Breaking and healing, followed by more breaking and then more healing... a cycle of death and rebirth, so to speak. All so that limits can be constantly crossed and the body gets used to the shock of breaking down internal barriers. During the opening of these points, speed, strength, reaction time, thoughts become very accelerated and it becomes almost instinctual to use such skills.
As the name implies, there are a total of eight gates inside the body that must be opened in sequence. Although it is unclear whether these openings have to follow a specific order, but during the war, Gai opened in the following order: Opening Gate 開門, Kaimon): located in the left hemisphere of the brain, removes the mental inhibition that prevents the use of force muscle. Opening this gate allows the use of Lotus Front. This technique makes the user tired more quickly. It's the sense of preservation of the human brain itself being deactivated, something I wouldn't have tried if it weren't for the anxiety I felt after the fight with Kakashi. Next comes the Gate of Healing/Rest (休門, Kyūmon): located in the other hemisphere, it increases the user's physical strength and re-energizes the body, allowing it to quickly recover from exhaustion; soon after comes the gate of Life 生門, Seimon): located in the spinal cord, it gives a reddish color to the user's skin and increases the blood flow in the body. Allows the use of Lotus Reverse. The Gate of Pain (傷門, Shōmon): Also in the medulla, this gate increases the user's speed. At this point the muscles begin to tear internally and there may be mucosal bleeding. The Boundary/Close Gate (杜門, Tomon): located in the abdomen, increases the user's physical strength. Bones begin to fracture. Gate of Vision (景門, Keimon): located in the stomach, increases all user abilities. The power emanated is enough to displace bodies of water and the user gains a green aura. Allows the use of the Peacock of the Morning, where the punches are so fast that friction with the air creates flames in the user's fists. Gate of Wonder/Shock (驚門, Kyōmon): Located under the stomach, causes the user to secrete blue sweat, which is immediately vaporized by body temperature and creates an aura that is often confused with chakra. Allows the use of the Daytime Tiger, a punch so powerful it creates a blast of compressed air. By opening this gate, the muscle fibers begin to break, causing immense pain at any touch the user receives and finally the Gate of Death (死門, Shimon): located in the heart, the user needs to pierce the chest with the thumb to direct the chakra to the location. The heart starts pumping at maximum speed, ensuring a physical power one hundred times greater than the maximum level. The blood starts to evaporate and causes a flaming red aura. The most powerful techniques are allowed, such as the Nightfall Elephant and Night Guy. Under normal conditions, the user's temperature is so high that he is cooked from the inside to ash.
This whole technique was a problematic thing and almost no return on investment. I mean, years of training, breaking the body over and over again just to temporarily glow and die. It wasn't a technique worth my attention under normal conditions, but... I wasn't normal. My shinkki were perfect for training in this technique. If I used Kouki (Kimimaru) while opening the first 4 gates, my body under stress would refine every second of this state. Add to that my natural regeneration and I'll make this 4-gate open state so easy that I could keep it open permanently.
But that's only if I follow the same order that Gai did. If I opened the Gate of Healing first and then the Gates of Pain and Limit... Wouldn't the healing nullify or at least help mitigate the effects of the last two gates? What if I opened the Gate of Healing followed by the Gate of Death? Would not the state of death be nullified?
Thinking about it, it would be the most viable method. While one gate regenerates and re-energizes the other breaks and destroys. In this state of healing followed by breaking my body would increase more and more its stamina and raw power. I wouldn't even need to use gates in a fight if my body in its normal state was already strong enough to handle a Gai with all the gates open. It was difficult. But not impossible. Lets do this.