A monster from birth, with no parents at least those were the stories, and dumped like trash into the slums of Kirigakure. A life unfit for that of an infant, was he an infant at that time, or was he a young child? Even he doesn't recall his most early years of life, leaving his own origins a mystery, a monster child is what they called him on the streets. Of course they were scared, disgusted, confused on how such a child could be born? It didn't ever bother him the way he looked, he basked in the fact, he was unique, and not alike any of the other children among the streets. The life of an orphan was a tough one, constantly battling for shelter, food, and even allies. A life that eventually painted his soul with doubt, doubt in the world, and while it eventually faded he carried a flame of anger towards the world for most of his youth til he was placed into an orphanage, more so forced, but it was a time he more so didn't enjoy a bit. It was the day-to-day ridicule, name calling, and bullying (which did not happen as often) that irritated him to no end. These struggles only drove him to his natural violent urges landing him in trouble when outbursts occurred. He didn't care for those he hurt, they hurt him first, and that to him was fair game. It eventually got the point he had a whole opposite schedule of anyone within the orphanage to stop any 'outburst' yet it didn't work much like their crude sense of discipline.
Of course his life turned around once he saw opportunity to prove himself more then 'the Fish Freak'. The calling of a shinobi was pushed upon a few select orphans, only to be tools of war, and the pawns of the corrupt Kirigakure. They had just recovered from the Second Shinobi War, still feeling the stings of war, with another in the loom. The Academy was rather rough, the post-war traditions didn't allow for the weak, and it definitely produced fine shinobi. He just so happened to be one of them. Of course his life still wasn't free of struggle, dealing with ongoing ridicule from other classmates, one in particular that gained his eye Kieta. A former resident within the orphanage he resided in as a child, now a rival, and bully. This bond proved to strengthen the two, until the day came to graduate, and he fell to the blade of his rival.

It was the last time Keita will ever spew foul words at anyone, the former graduate lay upon the floor soaked head to toe in his own blood, and it was satisfying. His fellow students stared at him in horror, of course they did, he brutally killed a fellow comrade. Usually this would have been a major incident except Kisame was a talented shinobi. A prized asset Kirigakure couldn't loose. The incident was swept under the rug yet they kept a continued eye on Kisame monitoring him, by issuing him a trusted Kirigakure Shinobi, Fugaki Suikazan. A man much like himself in some regards which helped calm the boys inner struggle. He had two other teamates, who he really didn't care for, and he made it very well aware from day one. Without anything to hold him back he quickly grew to fame.
The thing with war is that it never changes. As the bells of war began to toll pondering his own fate in the world. The fate of a soldier, a pawn in the bigger scheme, and even as a newly promoted Jōnin he was a valuable asset. It was time for him to show his true nature, the monster inside was ready, and it wanted blood. Slaughtering in the name of his village, the nature in which he killed, and the over all state of the bodies earned him the moniker Monster of the Hidden Mist. Years of bloodshed finally came to an end his fame spread has likely spread across the Five Great Nations. With no more need for the Monster of the Hidden Mist, his life finally seemed to reach overall peace. Though who he 'truly' was still within his very soul this fate he knew couldn't escape. With those thoughts in mind he dived into various missions either given to him by his sensei, or even the village itself.

Deceit lined his world, filled every void in it, and it took hold spiraling his life into a state of disillusion. The one man who he trusted, took him in, built him up to be one of the most feared shinobi in Kirigakure, and tore him down all with one action. A mission is all it was supposed to be, get the intel, and do the job. Yet he formed a bond something he hadn't done in years and it was real. For once someone hadn't judged him for the way he looked, acted, or even led his life as shinobi. Of course what mission isn't right without disaster? Upon the discovery the secrets of the Cypher Division might fall into the hands of the mighty Konohgakure no Sato he made an ultimate call and cut down his comrades. Under the subtle instructions of his master Fugaki Suikazan. An unknown variable came out of this situation though, one managed to survive, but barely to even life long enough to tell the tale except to Fugaki. Faced with a chance to pardon himself of any future crime, such as his ongoing treason he used Kisame as the scapegoat, and it ended up booking him a one-way ticket to execution.

Shackled in a blood stained cell he recalled his entire life, what it meant, his destiny, and why it ended up this way. Stewing in his internal conflict for a few days with no news of when his life shall end. He made a decision, kill his master, and prove his innocence. Breaking free from his bonds, taking the lifes of those who stood in his way, snatching his equipment.
In the dark of night he managed to find his former master amidst the chaos. What would he do with him? He surely went out of his way to pin his own treachery against Kisame, kill him, or force the truth out? His anger consumed him, the battle of student against teacher ensued, and he had the upper-hand. Subduing his man he trusted with his life begging for the truth. What the man told him shattered his world, the anger he once held for the world ignited once more. Fugaku Suikazan of the Seven Swordsmen had lost his leverage, a swift downwards blow, and it was over his head was cut clean from his shoulders. There was no one to confirm this truth even if he had left him alive and with that in mind he swiped the legendary blade Samehada disappearing into the night.
What is a story without a happy ending? Does he get one of those? He was a criminal though he had eventually sent word to Kirigakure that proved his own innocence after hunting down everyone involved with Fugaki and slicing them into pieces. It didn't matter what Kirigakure thought of him now his ties to them were severed long time ago. Whether they believed him or not he was a criminal at the very best, his goal? He didn't really have one at this point he hadn't found his way since that night except survive. That is what he would do til he found the right path.