In an alternate dimension, there exists a place much like the earth but with some technology more advanced then ours, and some more primitive. This earth has a wide variety of civilizations, but the most dominant of all are the shinobi clans. They control the peace, and also sometimes cause war. The governments of the world rarley persuade them to do anything, even if rewared well. Presently there are about 4 or 5 major shinobi clans, and the most powerful but most respected of all is the Senzai clan. They have the most advanced technology in the shinobi world, but their rival clans arn't far behind them. The Senzai's long time rivals are the Ryuko clan, smaller in size by a considerable amount, but on occasion rally up smaller clans when a large scale war takes place to balance it.
The shinobi clans don't breed and train their own, instead they rely on scouter nin to look for potential candidates to join them, and they search the whole of the Earth. If the candidate accepts the offer, they undergo a thorough search, physically and mentally to check its not a spy from a rival clan. If they pickup even the slightest hint of a relation with another clan, they dismiss him/her immediately. After they pass the checks, they are sent to their clan's main village, and a usually secret, underground training area. If scouter nin of rival clans were to make contact, accidental or otherwise, they would usually engage in combat, sometimes to the death, for the sake of disabling or reducing the scouter nin of the rival clan. These battles are normally ignored by the main heads of the clans, since those scenarios are inevitable, even if they are at peace with one and another.
Present day, some members of the Senzai had suddenly developed a sickness that drains their stamina, and die if left with no cure. The heads of the Senzai clan ordered an investigation, and after they checked all their registered members, found no clues. Then, they were at peace with other clans, even the Ryuko, and asked if their clans had some members suffering the same sickness. Each clan wouldn't reveal if they had the sickness or not, and refused to be searched. Their reasons were stated to be because they believe they are innocent and the truce they made with other clans at the end of the last war, made sure not even a finger be lifted otherwise that would mean the truce be broken and chaotic war would ensue again. Which no clan desired because they have all barely recovered from a great war. The Senzai grew suspicious of the other clans, and why all of them except themselfs would admit they have certain members ill.
They had no choice but to execute a dangerous and highly secret campaign to find answers from each member in each and every clan. To achive their mission, they would have to break their own rules, where one wears a ninja gi that dosn't belong to them. They wore the clothes of Kumo, a defeated clan in the previous war, for two reasons. One was to confuse the member of a rival clan if they were caught, and two to hide their own identity. What the disguised Senzai members asked were if they knew why some of the Senzai clan members had this strange unknown illness, and asked if there was cures incase their barely surving clan would contract the same fate. These questions were a risk to ask incase of raising suspicion, but was the only way they could get information without forced interragation. They couldn't capture them, and try to interragate them since a shinobi would always give up its life instead of helping their enemy.
When the Ryuko and other clans heard that the Kumo were back from their defeat, and that they were asking questions too about the illness that struck the Senzai clan, they were confused. Because at about the same time the Ryuko members were coming back to report that the Kumo were asking them questions, they also got reports that the Kumo were attacking and sometimes even killing the Ryuko members. Why would they ask questions, and why would some kill they thought. The Senzai clan are known to be honourable shinobi, they wouldn't randomly kill other clans without reason during a truce. Not long after, a group of Ryuko ninja managed to ambush a sole Kumo ninja, and by chance one of the Ryuko members recognised the face of the Kumo when he was strip searched. The Ryuko announced that the Kumo they caught was really a Senzai ninja in disuguise, and when the heads of the Ryuko heard this, they immediately waged war with the Senzai clan. So far the war has lasted almost a decade and this where the stage of BladeBattles commences ...