A nation located somewhere in the Shinobi World that contains a treasure of mysteries. Little is known about this nation, including its location, composition, and environment. However, with recent events, pieces of history have begun to connect. In the middle of year 11 V.E., a large-scale operation known as Operation: Lust was conducted. The goal of this operation was to eliminate certain inhabitants from the face of the continent. This began a huge raging war that continues in the present day.

As the factions that hailed from Bujan began to traverse their way through the Main Land, members of an Iwagakure scouting patrol came across members of the Koseki in the Northern Hills. The Koseki explain their situation to Tsuchikage Ni Miyajima, who refuses to lend them their aid. However, shinobi from Sungakure and Konohagakure are more welcoming to the Hanasojo and Mizushinzen factions. Disagreements between the villages begin to rise after the handling of the mysterious factions becomes public. Tensions began to brew, but while the villages were talking about the disagreements, multiple lone forces sat quietly in the background. One of those forces goes by the name of Akei from the Hanasojo faction. The mysterious blindfolded figure had a strong connection with the sakura tree, and invited shinobi to partake in his meditation with him in hopes of gaining some source of newfound strength. Another one goes by the name of Kenta, a smart researcher from the Mizushinzen faction who cooperated with the Konohagakure and Kirigakure Research Divisions of various research topics. While these forces began to move, another loomed in the darkness. The factions and the villages scheduled a meeting, which was ambushed by none other than the Nezumiya. There were both shinobi and faction casualties as the Nezumiya made their presence known.

The Nezumiya unleash a reign of terror upon the Main Land, terrorizing the shinobi and civilians of each village. As the faction made their statement, a group of shinobi led by Kazekage Aetamos Yome were able to slaughter an important member of the Nezumiya, who turns out to be Alvus Houki. This sparks great confusion and unrest amongst the shinobi, as Alvus Houki was a known name that was in Main Land for quite some time. Who were the Nezumiya connected to? Who is Nezumiya? Upon this death, the Nezumiya make it known that they are open to allow shinobi to join their power cause. Three shinobi successfully make their way into the ranks. After their recruitment, the Nezumiya continued to bombard the nations with indirect terror, but then there was a change. The Nezumiya began to organize themselves, and they established a fortress in the Ancient Ruins.

During one of the Nezumiya's missions, they were able to capture two councilmen from Sungakure: Elite Oribe and Raiden Yuki. In another mission, they were also able to capture Jonin FarmerTom Lee from Konohagakure. The kages of each of the villages banded together to create a Great Shinobi Alliance in an attempt to save the three individuals. The Nezumiya fortress contains a nearly indestructible door with no way of opening, however, so the alliance had no leads as to how they were to save their comrades. Enter Toshio, a mysterious man within the ranks of the Nezumiya who gave the shinobi a chance. He created a series of riddles for the shinobi to solve, and if they were correct, they would be able to open the door temporarily to find their friends. The shinobi were successful in completing said riddles and were able to continue with the operation. On one fruitful day, the Great Shinobi Alliance stormed into the fortress of the Nezumiya. But, they did not go in without any resistance. Multiple casualties were suffered on both sides, and only one of the three individuals in question was able to survive the major battle.

Following the previous operation, the shinobi were full of hatred towards the Nezumiya, who attempted to take a step back within their fortress to regroup. However, Kazekage Massimo Yome had other plans. He rallied up the alliance once more to fight the Nezumiya in multiple waves, resulting in many casualties on both sides, including Kenta. An important figure within the Nezumiya, Commander Shuen Iwatsuki, showed face. With his appearance, some shinobi began to question his tactics and why he would continue his pursuit of revenge. The battle was over, so why continue to fight? More questions continued to arise as a member of the Land of Mountains, Alonza Uzumaki, was killed, and with his Amulet being taken alongside it.

After the operation concluded, the shinobi felt helpless. What can we do? Is there any hope? It didn't help either that Iwagakure's Akai Utsuwa was also taken by the Nezumiya. Luckily, there was nothing to worry about. Throughout a couple of months in the Shinobi World, it seemed that the factions disappeared. Where did they go? What happened to them?

This operation was started in 16 V.E. by a former Kirigakure Anbu named Flame. With the help of the shinobi, they were able to find information about a mysterious substance named Morikami Moya, which is found inside the Nezumiya Fortress. The shinobi and Flame used this information to try and formulate a counterattack against a dormant Nezumiya. After months of a mysterious disappearance, the shinobi reunite with Flame and Hinizami, the wife of the deceased Kenta. They band together to create the Core Operation, which is dedicated to finally defeating the Nezumiya.