(Before reading this chapter, here is a fan theory. After all, it's a free novel, so just enjoy the story and creative thinking!)
Mei Terumi once said during her fight with Sasuke that she possessed water, earth, and fire chakra, which allowed her to use the Lava Release and Boil Release Kekkei Genkai.
But what's the reality? Lava Release manifests as corrosive water, and Boil Release as corrosive mist. Both are essentially based on the corrosive properties of water, combined with earth and fire chakra to create corrosive Kekkei Genkai.
As we all know, Kekkei Genkai can be inherited through bloodlines. While they can also be developed later in life, given Mei Terumi's age and the environment of the Hidden Mist Village at the time, it seems unlikely she developed two Kekkei Genkai.
If it were that easy, Hiruzen Sarutobi, with his mastery of all elements and the title "Professor of Ninjutsu," having lived for so long, should have been able to create not only Kekkei Genkai but perhaps even Kekkei Mōra!
Yet, all he had was the Great Art of the Mystic Leaf, and nothing more!
Therefore, the author has established a setting where the Terumi clan possesses the Lava Release Kekkei Genkai as an inherited trait.
This is referenced by the Kekkei Genkai situations in various ninja villages: The Hidden Cloud Village, with its constant thunder, gave rise to Troy, a ninja with Magnetic Release who could control magnetism, and Dodai, who developed Boil Release, an extremely explosive Kekkei Genkai, into Rubber Release.
The Land of Wind, with its perennial high temperatures and drought, produced Pakura, a ninja with Scorch Release who could desiccate humans into mummies. And the past Kazekages who mastered Magnetic Release based on the chakra nature of the One-Tail.
The Hidden Mist Village possesses the Six-Tails, and since there hasn't been a suitable jinchuriki for it, conflicts with the Hidden Mist ninjas have undoubtedly occurred. So, it's quite reasonable for the Terumi clan, as members of the Hidden Mist, to have developed Lava Release over the years by studying the Six-Tails' ability to spray acid, right?
However, Mei Terumi herself possesses fire chakra in addition to others. Based on the nature of Lava Release, she replaced the earth element with fire, thus semi-developing Boil Release.
(After a lot of rambling, the intention is to find a reason for a setting that might not be accepted by readers. Let's discuss rationally and refrain from harsh criticism!)
...
There is a peculiar place in the ninja world.
A small, isolated island, not very large, yet home to a ninja armed force that holds significant influence in the ninja world.
The number of ninjas is not large, but almost every one of them is an elite.
The Hozuki clan, skilled in the Water Transformation Secret Technique; the Kaguya clan, born for battle, with the Shikotsumyaku; the Yuki clan, who mastered the Ice Release Kekkei Genkai...
And the Terumi clan, who, inspired by the Six-Tails, a giant slug covered in strong acid, developed the Lava Release Kekkei Genkai, a powerful acid jutsu combining water and earth properties.
This force has almost no contact with the outside world, relying solely on the abundant resources of the surrounding seas for self-sufficiency.
They even keep two rare Tailed Beasts in captivity.
This place is none other than the Hidden Mist Village of the Land of Water, known by the moniker "Village of the Bloody Mist."
The Land of Water is located far overseas. Apart from the dozen or so smaller islands surrounding the main island, its borders do not adjoin any other ninja nations.
The closest country with a name that can be mentioned is an inconspicuous small country situated between the Land of Water and the Land of Fire, with a territory of only four small islands, called the Land of Sea.
...
The recent events in Konoha have shaken the entire ninja world.
Therefore, upon receiving the invitation from Konoha to hold a joint Chunin Promotion Exam for the ninja world in a month, all nations, big and small, regardless of their motives, began to take action.
Except for the Land of Water!
And so, Orochimaru personally came.
The current title of "Village of the Bloody Mist" for the Hidden Mist Village is not a pleasant one. Apart from some fishermen living along the coasts of the Land of Fire and the Land of汤, who are forced to go out to sea to fish out of necessity.
Even those merchants who would risk their lives for profit dare not venture into these waters.
If they can kill their own comrades without hesitation, what chance do ordinary people have against them?
Therefore, finding a ship from the coast of the Land of Fire to the Land of Water would be harder than climbing to heaven.
However, this is not a problem for Orochimaru.
He can fly!
...
The Third Mizukage hailed from the Yuki clan and his given name was Mu.
His name was similar to Mu, the Second Tsuchikage of the Hidden Stone Village, but the Second Tsuchikage Mu was the murderer of the Third Mizukage Yuki Mu's master.
The Second Mizukage of the Hidden Mist Village, Hozuki Gengetsu, who perished simultaneously with the Second Tsuchikage at the end of the First Great Ninja War, was Yuki Mu's esteemed teacher.
After the simultaneous demise of the two Second Kage, the Hidden Mist Village, which had been solely supported by the Second Mizukage, was unable to continue fighting and had to retreat to the Land of Water.
Yuki Mu ascended to power.
To make the Hidden Mist Village stronger, and to have a chance to return to the mainland and avenge his master. This man, who appeared gentle and elegant, inherited the unfinished wish of the Second Mizukage Hozuki Gengetsu and took over the training of the Seven Ninja Swordsmen of the Mist.
At the same time, he ushered in the bloody and terrifying era of the Village of the Bloody Mist for the Hidden Mist Village.
He firmly believed that only through such a process of survival of the fittest, where the strong prey on the weak, could the Hidden Mist be forged into a powerful ninja village with all elites.
As for the ninjas who died in the struggle...
The weak were not worthy of living in this wolf-like village.
Rather than letting them die humiliatingly at the hands of enemy ninjas later, it was better to let them become nourishment for the growth of the stronger members of the Hidden Mist Village from the genin stage.
There were voices of opposition at first.
However, when all the Kekkei Genkai families and the Third Mizukage united, all opposition voices vanished.
Of course, this would plant hidden dangers within the Hidden Mist Village, but the Third Mizukage paid it no mind.
As long as the next Mizukage possessed the same strength and strong will as him, the Village of the Bloody Mist could continue to prosper.
"Yagura, inform the teachers at the ninja academy that this year's graduation exam can begin!"
Yuki Mu slightly opened his squinted eyes, glancing at the sky outside the window, and softly instructed his disciple standing beside him.
"Yes, Master!"
Kusagakure Yagura, whose body had not yet fully developed, bowed respectfully to Yuki Mu, placed his hand on the coral staff behind him, and calmly walked out of the Mizukage's office.
Below the platform, three expressionless Hidden Mist ninjas stood at intervals, each followed by dozens of children from the Hidden Mist Village who were about to participate in the graduation exam.
The expressions on these children's faces varied.
Some cast cold gazes at their companions, their eyes occasionally lingering on the weak points of the opponent's body, as if contemplating where to strike to eliminate them in the shortest possible time.
Those who were met with such gazes either glared back and made a chopping motion with their hands at their necks, or remained expressionless with disdainful eyes...
Of course, there were also those who trembled and could barely stand steady, almost scared to death.
No one paid attention to these individuals, nor did anyone show pity.
Yagura looked at the three formations below and calmly called out to an empty space beside him:
"Mangetsu!"
The sound of flowing water echoed, and the thin mist dispersed around the Mizukage's office rapidly condensed into a fifteen or sixteen-year-old boy beside Kusagakure Yagura.
Hozuki Mangetsu grinned, revealing his pointed teeth, pulled out a large scroll from his stomach, and unrolled it with a playful smile in front of Yagura.
"Aside from the Hozuki clan, it's truly difficult to find individuals who are compatible with these seven ninja swords."
"The Mizukage-sama has invested so much effort. I hope for a good result this time!"
Yagura nodded, his voice softening slightly.
"Thank you for your trouble!"
"The Mizukage-sama said..."
"It can begin!"
Hozuki Mangetsu cheerfully waved his hand over the scroll, and seven uniquely shaped ninja swords were instantly summoned from the scroll.
Kabutowari, the blunt sword
Kiba, the lightning blade
Samehada, the shark skin
Kubikiribōchō, the executioner's blade
Shibuki, the explosive blade
Hiramekarei, the twin blades
Nuibari, the needle sword
Hozuki Mangetsu casually waved his hand, and seven streams of water surged from him, carrying the seven ninja swords and flying into the open ground below.
"The three of you, it's up to you!"
The three Hidden Mist upper-level ninjas looked at the swords firmly planted in the center, exchanged glances, and nodded in unison. They simultaneously performed the Body Flicker Technique and leaped to the rear of their respective teams, raising their hands and forming a string of hand seals in perfect unison.
"Water Style - Joined Water Prison Technique!"
A transparent water barrier, created by the combined efforts of the three upper-level ninjas, rose from the ground, instantly forming a massive cage that enclosed the more than a hundred children.
Kusagakure Yagura, watching the children who fell into chaos as the seven ninja swords appeared and the water prison rose, calmly announced the topic for this year's graduation exam.
"End this trial before the air you can breathe is depleted."
"The number of graduates this time..."
"Seven!"