The grudge between Yroth and Gray started a while back. At that time, four years ago, Gray was only a Major ranked soldier. He was already leading, at that time, the number one special operations team in Country Z.
He was looking for clues on the infamous drug cartel, The Saints. The mastermind and leader of this cartel was none other than Yroth. Back then, they didn't have an inkling on who exactly was the mastermind behind the operation.
The only clue the military had was that there was a supplier deeply rooted in a highschool in Country Z. Gray spreaded his team members out to the different highschools as staff members. He himself was tasked with being undercover in the top high school, Metropolitan Academy of Science in Country Z.
The undercover process was long and arduous. They were not allowed to reveal their identities to the public for fear of the cartel group hiding in the dark. At that point, it would be like finding a needle in a haystack.
During the day, Gray would be a Mathematics teacher to one of the classes. In the night, he would rendezvous with his team members and get information (if they possessed any) from them. The process repeated itself for a whole year.
...
When Sato was 16, he had went to Metropolitan Academy of Science (MAS). He had a rough highschool time as he was bullied by his schoolmates. From young, Sato was already deemed as the genius student in the school. Everyday, the rich students would exhibit their power on Sato and threatened him to help them complete their assignments. Sato was on scholarship into MAS and so, he didn't dare to disobey.
In his toughest times, Sato met and got to know this school teacher. The man was wonderful and helped him through his tough times. The teacher was Gray. It was also this time when Gray met the young student, Sato who back then only knew him as a teacher. .
Every test that Gray set for the class, only Sato was able to get 100%. Yet, there was never a look of cockiness or arrogance in the boy. In fact, Sato always looked serious in his class.
One day when Gray was going back to his office, he noticed Sato being taken to the back of the school by a group of boys. Sato looked afraid.
Even though Gray was doing an undercover mission, he took his fake job very seriously. Knowing that something wasn't right, Gray went to take a look.
It turned out that Sato had accidentally not changed the answers on the bully's paper and so he was caught for plagerism. The rich bullies decided to take turns to throw punches at Sato. By the time Gray arrived, Sato laid sprawled on the ground, unconscious. Gray took pity for him and carried him to the infirmary.
The nurse treated his wounds while Gray sat beside the youth as he recuperated. When Sato woke up, Gray enquired about his predicament. At first, Sato was afraid to say anything and didn't dare to reveal the problem. However, after months of care from Gray, they eventually got close enough for Sato tell him everything.
The next day, the Sato's bullies were expelled effective immediately. They were not even given a chance to repent. All these were thanks to the Tobion family's power. Of course, Sato knew nothing of it and thought that the school did everything.
After the bullies were gone, Sato's school life had improved dramatically. He even made two close friends that would eat meals and hang out with him.
In addition, Gray's and Sato's relationship took a turn for the better. Gray had fallen in love with Sato. Sato had fallen in love with Gray. Though there was the thing about teacher and student relationships, they didn't let it hinder their learning or teaching experience. Gray also continued his undercover mission even during their relationship.
In the end, after a year of hard work, on Gray's side, he finally managed to gain valuable information that there would be a supply overhaul coming in on the coming Saturday night. The head boss of The Saints was taking a visit that day too.
Hence, that day, the Special Ops team led by Gray, headed off into the blackness. Armed and ready, they scouted for the cartel's presence. At 11.45, close to midnight, a black limousine was sighted circling into the meeting point. A man dressed in a white suit, with neon green spiked-up hair. He was Yroth, the drug cartel lord.
When the target was spotted, the team moved out effectively neutralising the threat. However, the drug cartel members were also armed with firearms. They fought back in hopes that Yroth could leave unscathed. It came true. The leader made his solo escape.
Though Yroth left, he was still trapped within the four walls of Country Z. Sea patrol and air control was tight. Thus, the search for Yroth began by the authorities. Gray and his special force team had finished their mission and could wrap up loose ends.
This marked the beginning of the end. It spelled out that the days of Gray being Sato's teacher started to dwindle away.
Till now, Sato knew nothing about this mysterious teacher/ lover of his. He only knew that Gray was great to him. And that was all he asked for.
During the last few days in school, Sato and Gray spent their usual time together after school. Gray had allowed Sato to stayover at his house where they simply cuddled and relaxed together. That was when the remains of the Saints attacked and ambushed Gray's home. For some reason, Gray's location and identity got leaked. The event resulted in Sato losing his memories of the past, while Gray got a service injury.
By the end of it all, Yroth was finally arrested but had to be extradited back to his home country, Country H for stand trial. He was then sentenced to life imprisonment, but it seemed that the stay in the prison didn't last for too long before he broke out.