Following Jack's near-death accident where he awakened not just the memories of another version of himself and the Abyssal Eclipse Gear, he used it repeatedly. He quickly became addicted to feeling himself improve in real time.
Subjects that he should struggle with like Japanese and advanced levels of math were made much simpler by his accelerated thought process. That was just the mental side of things as constant use of his Sacred Gear also passively led to him having a stronger body.
The Boost that Apophis stole from Ddraig wasn't the only power the Evil Dragon had. The main one was the extreme levels of Darkness manipulation. His Darkness could dissolve anything he designated and absorb attacks from others.
He didn't just control the shadows, but he could also form what Apophis referred to as Primordial Water. It was a massive amount of Liquid Darkness which was extremely deadly and capable of dissolving anything that it came in contact with.
When Apophis used it, it was deadly enough to wound God-class beings and Issei's Diabolos Dragon. That armor was what did Apophis in, but it wasn't an easy fight even for Issei at his best.
Jack, taking the example was determined to measure up to Apophis and the Issei in his memories. With constant use, his limits as a result of his age and race were being undone. Mana constantly flowed through him passively making him more durable, faster, and even smarter.
Putting effort into something that wasn't fun was hard because you didn't see results immediately. Training with a Sacred Gear changed that because you would always see results and want to keep improving.
That was how Jack was now as he would sometimes train not just once a day, but twice. To be able to endure even more power, he began to do Calisthenic Training and some light Weight Training with his Father's weights.
His Father while concerned became fully supportive as Jack proved to be strong. This made Jack Sir feel that he found something he and his son could better bond over. Together, early in the morning, the two would do calisthenics or weight training.
So Jack didn't hurt himself, his Father made sure to keep an eye on him, but it was unnecessary. Through the enhanced recovery speed of his Boosts, he didn't need rest days just more protein-rich meals.
After his workouts, showers, and eating, he would go back to his room to continue his studying while Boosting. With three Boosts, his recovery speed was enhanced by a factor of eight which is why his caloric intake had increased.
Apophis was also focused on completely reverse engineering the Boosting of Ddraig. Each time that Jack used it, he put most of his efforts into figuring out how it worked.
In less than two weeks of training, his body despite being eight, was much more durable. He even began to develop some increased muscle definition, his bones were growing denser and he could Boost up to four times increasing his attributes by 16.
That made his thought speed, recovery time, mana, and all his other abillities by 16. Even if it was temporary it allowed him to learn the Japanese language and several advanced forms of math in three weeks. Two of those weeks had been with three Boosts and the last week with Four.
Four was much more efficient than three and five would be even faster than that. However, five was the hard limit Apophis set for the moment until he could fully reverse-engineer it. When he finally returned to school, he was a different beast. He went from an illiterate foreigner to the top of the school.
It shocked his teachers and Aya especially who always had to help him. Now, he could fluently speak Japanese, write, and read it as if it were English. With his increased grade level, he applied to the football team as he had been in Texas.
Aya who was one of the best female track students was happy for him. However, it was almost unfair as he was superior and much bigger than the Japanese boys who at age 8 averaged from 4'1-4'3(125 CM-130 CM).
As for him at age 8 he was 5 foot tall(152 CM) meaning he was a foot taller than the other boys. With his training with his Father and his Sacred Gear, he quickly became the best player on the team.
Not only did he seemingly overnight become one of the smartest students, but also the best player on the football team. His Mother and Father were so impressed with his improving grades that they wanted to reward him.
When his parents asked him what was it he wanted, he thought about it as if he could get a phone, or some other expensive electronic. However, he decided to just get a new pet because he didn't want one.
Hearing that he wanted a pet, his parents were ok with the idea. They asked what he wanted and he went with a Maine Coon kitten. His Mother loved the idea and his Father just gave him a speech about it would be his job to take care of it.
Jack accepted his responsibility and since he did improve his grades so much, his Father did end up buying him a Maine Coon a few days later. Now, three weeks and five days after his accident and awakening, Jack was sitting on the living room couch looking at the small fluffy creature in a cardboard box.
His Father had spent 2,800 dollars American or 4,023,13 Yen to buy the kitten. For a man with an income in the six figures, he had money to spare. Especially when his son was doing so well after his accident.
Jack reached down into the box and pulled out the little kitten which was dark black and silver. He smiled as he gently stroked the kitten's head causing her to close her eyes.
"Dad, I love her."
Jack Sir smiled as he could see his son and wife were both swooning. Esmeralda was sitting next to her son looking at the kitten in his arms.
"Sweetie, she is like a ball of silk. I want one too."
Jack Sir stopped smiling.
"At least let this one grow up, dear."
Esmeralda pouted.
"Please, Honey."
Jack Sir raised his head faking like he was thinking.
"I don't know, one kitten is a lot especially a Maine Coon. They will get so big, and you know how things are right now. Unless."
He got a funny look on his face which Esmeralda noticed. She glanced at Jack before smiling.
"Sweetie, why don't you go to your room? Your Father and I need to talk."
Jack had a suspicion that this was not about a cat. He didn't even need to be told twice as he quickly escaped to his room. In the meantime, his Mother dragged his Father to the beddroom which thankfully had thick walls.
There, she 'convinced' her husband to get her a kitten as well. As for Jack Sir, well in exchange he just wanted another baby. While his parents were working on a small sibling, Jack closed his door and locked it. He sighed in relief as his other selve memories worked against him as he knew everything now.
"Gross."
[Get over it. As the Abyssal Eclipse Emperor you are going to be surrounded by women. If Issei with all his faults had a harem you are going to be involved with plenty of female partners.]
"I am still 8 Apophis."
[Who cares? You already got your first potential girlfriend. That Aya girl since she is a cutie. Don't you want her?]
Jack seemed confused so he set the kitten down on his bed.
"I am still eight."
[You didn't answer the question.]
Jack did think about it.
"I don't know, maybe, but I am too young right now. Give me a few years."
[That is fair, anyway, what will you name the kitten?]
Jack looked at the kitten that was running across his room.
"I think I am calling her Amara, it is a cool name after all."
[Not bad in my opinion. You know, this is a good chance. I can teach you how to make her your familiar. By doing that not only will she feed on your Mana, but she may even be able to fight for you in the future.]
"Cool."
[Exactly. I will transfer the spell as in my long life I was second best behind Azi Dahaka in Magic.]
Apophis proceeded to transfer the proper ritual circle that was needed. Once he knew it, Jack nodded to himself as he held his hand out before he took control of his Mana. He focused on the past three weeks of nonstop studying math to get mana control.
His mana began to flow out of his body and it started forming a black spell circle. He focused on forming the circle, but as it was his first time it fell apart.
[You can Boost to make this easier.]
"I need to be able to do this without Boosting. I got this."
He remembered the feeling of Boosting and enhancing his abilities. He began to circulate Mana through his body which passively caused his thoughts to speed up. Amara watched on with fascination as pretty lights kept flashing in the air.
The spell formation only fell apart three times as by the fourth time he formed it perfectly. He did it once more to get more familiar with it which caused the spell circle to form perfectly and in a few moments.
"I got it."
[I am impressed, it takes most human mages several days at least to form a single spell. You continue to impress me, my friend.]
"Thank you, Apophis, now then."
He walked over to Amara and held his hand out to her. He then repeated the process and formed the familiar spell which formed into a small orb of Mana that entered the head of the kitten.
When that happened, the Kitten glowed black and red for a few moments as Jack's Mana was flowing through her body. The bond between Jack and his new familiar formed perfectly and would grow deeper as time went on.
When it was over, Amara didn't look any different, but now his Mana would passively flow into her from their contract.
[In time, this kitten will become an impressive creature.]
"Cool. Thank you.]
[No problem. It wasn't that big a deal.]
Jack smiled.
"Sure. Thanks, pall."
Regardless, Jack lay on his bed with Amara curling up with him. She was sleepy as mana exposure was a good feeling, but it could be tiring. While she grew used to Mana something new in her body, being up with her contractor would be for the best.
As for Jack, he had been training nonstop for three weeks so he deserved a break. He closed his eyes and fell asleep as he needed to rest. While he and Amara snoozed away, their new contract began to stabilize as they became closer to each other.
Following this day, Jack now along with his little ball of mischief continued his training under Apophis. Without his Father knowing, he pushed himself harder than before in training. He lifted much heavier weights, and he pushed himself with weights during his calisthenic workouts in the early morning.
After showering and eating he would recover through the Boost allowing him to improve in a couple of minutes.
While he recovered, he used the Thought Acceleration of his Boosts to go through the memories of Apophis and the other Jack. Especially the ones where he learned magic. Through their experiences, and Apophis' teachings his mastery of Human Magic was improving.
Since his body had improved in quality, he could push himself past 4 Boosts and went to 5. That meant that his Thoughts got accelerated by a factor of 32 making his recovery and studying supernaturally fast.
What would take a normal talented Witch or Wizard days to learn, he could get done in minutes. Through the experiences of his other self, he picked up some elemental spells. Like Fire Ball, Frost Blast, Lightning Strike, Stone Surge, or Water Spear.
He even got some buffing spells like Speed Acceleration, Reinforcement, and Mana Coating. He had an easier time with Darkness Magic and Fire Magic than the others, but the benefit of Human Magic was that with the right calculations, no element or magic was off limits. Something that even he didn't take into account was that by pushing his body he was growing larger and taller faster.
He was already the tallest kid in his elementary school, and he was going to become the largest too. When he wasn't in his training he was hanging out with Aya at his house or hers with Amara.
Aya and her parents took note of his growth spurt, but they just noted that to Jack Sir who was a giant by Japanese standards. This was how he spent the next two years secretly training himself.
Two years with his drive for improvement had greatly impressed Apophis as most hosts at age 10 hadn't even awoken their Sacred Gears. As for Jack, at age 10 he was already 5'7 which made him the average height of most Japanese men.
Of course, compared to his Father he still had a lot of growing to do, but in terms of sheer strength, he was beyond Superhuman. He could bench 10 tons with minor effort, he could sprint at 150 mph, and in terms of magic, he could decimate a block with his more destructive spells.
That was not taking his mastery of his Sacred Gear into account as he was a dangerous individual for any supernatural monster. Speaking of the Supernatural, the stronger Jack became, the more he could feel more eyes on him.
It was becoming annoying, but they had been too afraid or apprehensive to approach. However, they were, they would be in for a surprise if they put his family in danger.