At the border of the Land of Rain.
The unceasing rainfall had soaked this land into a muddy mess.
Several Amegakure shinobi wearing breathing masks stood guard atop a border watchtower, bored out of their minds.
"The border's been too quiet lately," one rain shinobi complained. "There hasn't even been a smuggling caravan."
"Lord Pain issued the highest alert order. Who would dare cause trouble at a time like this?" another rain shinobi said, shrinking his neck.
Suddenly, the pooled water on the ground began to tremble faintly.
A dull roar, like thunder, came from the distant curtain of rain.
"What was that?"
The rain shinobi rose warily and looked toward the border.
Through the gray rain curtain, a row of black steel troops was slowly advancing.
They did not belong to any shinobi village force they recognized.
They wore uniform black tactical rain capes, no forehead protectors, and expressionless metal masks over their faces.
The weapons in their hands were neither kunai nor shuriken, but a new model of Bolter.
"Stop! This is the territory of the Land of Rain!"
The rain shinobi captain shouted as he pulled an Explosive Tag kunai from his ninja tool pouch.
"Come any closer and we'll attack!"
The black-clad force did not stop. They maintained their perfectly synchronized march, like emotionless machines.
"Fire a warning shot!"
The rain shinobi captain hurled his kunai.
Boom!
The Explosive Tag detonated more than ten meters in front of the black force, spraying mud and water everywhere.
It was merely a signal.
The next second, the black formation at the front abruptly stopped.
They raised their Bolters in perfect unison.
"What are those? Could they be..." A powerful sense of dread rose in the rain shinobi captain's heart.
He never got the chance to find out.
"Ready—fire!"