After 4 years at the school Cain left after graduating but the detective wasn't there to see him off. He was at home with his father as his mother was found dead in their house the previous evening. The detective was so upset that he didn't leave his mother's room for 3 whole days. His father didn't know what to say to his son as he knew he must have been going through a hard time. The detective left the martial arts school, before graduating, after police investigators came to the conclusion that his mother was murdered, and that the killer had got away.
The detective then trained to become an officer and after becoming one he quickly climbed the ranks until his was made a detective. A detective was a very well known and respected title within the police force as it meant you had been recognised as one of the strongest or most intelligent officers. In the detective's case he was well known throughout the force as one of the most intelligent officers, because he would find clues that no one else would ever find in a short amount of time and he was also known as one of the strongest because of his martial arts background. The reason the detective was so good at his job was because he had a drive and motive to find the person who had killed his mother. He wanted revenge.
After years on the force the detective had put together enough evidence and found enough witnesses that he was funded by a high ranking investigating agency because what he was finding was related to their case. He declined their assistance at first because it was something very personal to him, but then people started coming to kill him as he was getting too close to the truth. After these assassination attempts happened the detective accepted the agency's help and was given support by high ranking government officials from around the world.
The detective was then filled in about an organisation that threatened the entirety of the world. The detective didn't really care about them until the agency informed him that the person behind his mother's murder was apart of the organisation. He then accepted to help them take down the organisation as long they gave him all the information they had on the person behind his mom's murder and that he would be the one to take them down.
The detective eventually found the culprit behind his mother's murder. He was about to kill him but then remembered that he could ask him about the organisation to repay his debt to the agency. The culprit told the detective something unexpected during the interrogation, "I am sorry that your mother died but I was told to do it otherwise I was going to die." The detective asked, "Why would you die?" and the culprit responded with, "I made a mistake, and this was to make up for it."
The Detective was confused and angry as to why his mother had to die for this man before him to survive. The culprit then looked at him and said, "I am sorry that I killed her. It wasn't even supposed to be my job. I was just given it by the head of the organisation because it was a big enough job to save myself?"
The detective grabbed him by his collar and threw him against a wall, "Then who told you to kill my mother? Why did she have to die so that a scum bag like you could survive? Tell me! Why did it have to be her?" The detective started crying as the agency's agents pulled him away.
After he left the culprit made a full confession to the murder and how he was forced into it by the organisation. The Agency asked for the head of the organisation's name, but he couldn't tell them because he didn't know as he was just a small fry of the organisation and wouldn't be trusted with information like that.
He then told them that the only people in the world that would know that information were the top officials of the organisation, but it was unlikely that they would tell as they were extremely loyal to the organisation and the head of it.
After the Agency confirmed all the information they were given they told the detective that this may have been the culprit who physically killed your mother but there was someone else who wanted her dead. The detective was upset as he had been searching his whole life for the wrong person. The detective then agreed to fully investigate the organisation and help the Agency in taking them down.
He then went off to train with professionals in stealth missions so that he could sneak in and out of places without being known. The detective's identity was then kept hidden so that there could be no leverage on him, and he started being called the Samurai detective as he was a detective and he made swords his main weapon.
He then received valuable swords from the Agency and his grandfather to use in battle. The sword from the Agency was from some ancient swordsman that was once called the greatest in the world, the sword from his grandfather was one that was handed down throughout their family. It was supposedly given to one of their ancestors by an almighty being.
The reason for this was lost through the generations and his grandfather isn't even sure if it was a god or not, all he knows is that that sword holds great power and was looked after by their family for many generations, so it must be of some significant value.