Conquering the Mythos: Reincarnated with SSS Rank Skill Corruption

They stood like that together, two souls who had gained and lost so much in a short time, for what felt like forever.
Even with the happiness Kai felt knowing that Ernest was safe, he couldn't help but curse the world for causing so much pain to a young, innocent person.
'She's 6. She's supposed to be running around annoying us with her constant energy. She's supposed to refuse to eat her greens. She's supposed to pester us with questions about everything and anything. Instead...'
He closed his eyes, refusing to see the horrible sight of her tears. Instead, she had to watch her brother die.
And even though she was young, she knew it was her fault.
"I- I'll never be bad again! I p-promise! I'll... I'll just be the bestest little girl daddy could ever want. I- I don't want to be bad again! I don't wanna lose you, Kai!"
These words that stormed through her sobs penetrated Kai with every syllable, leaving him paralyzed.
Unable to move or think, he just shook his head.
"It's ok. You didn't know better. This is my fault."
Ernest violently threw her head back and forth, vehemently disagreeing with Kai's reassurance. "No! No, no! It's not your fault Kai! I'm a bad girl, and now my brother is dead!"
Raising his head to the sky, Kai scorned the earth as he cursed all the gods.
Then, he picked up Ernest, trying to ignore her screams.
"No! Kai, Kai, we can't leave him here! He- brother needs a proper burial!"
"There's nothing left to bury, Est."
...
"My son died fighting the beast?" Shuzen asked yet again.
Shortly after Khazi returned to the woods, sacrificing himself, Shuzen had returned from his hunt. It was as if the cruelest twists of fate occurred one after another that day.
Kai nodded his head, trying to ignore the wailing screams of Ernest as his mother bathed the blood off of her: Khazi's blood.
Shuzen turned to a cupboard, pulling out 2 apples with a quick jerk of his arm. Kai jumped as he slammed the door shut.
"That's his blood covering you?" Shuzen asked as he threw an apple to Kai.
Kai's reflexes kicked in, causing him to catch the apple. And smear it with blood.
Even as he looked at it with disgust, he held onto the apple, already knowing where Shuzen was going with this.
Shuzen took a bite of his own pure apple before saying, "Was my son the one who tamed the beast? Did he die defending his sister?"
Before answering, Kai took note of each characteristic of Shuzen before responding. His casual tone completely betrayed the weight of his loss. He was leaning on a counter with a complete lack of dignity, as though he was a Baka. When he bit into his apple, he took no care to keep his face clean from the juice.
His robe wasn't fitted, his eyes held no heavy baggage associated with grief.
Instead, they were sharp, calculating.
Kai knew the truth then.
Shuzen didn't really care his son had died. He was only looking for a way to gain power after the loss of his heir.
'But does he want me to be the heir or the scapegoat?' Kai thought to himself, knowing his and his mother's life were in this man's hands.
Up until this point, Kai was just a weak, even if bright, elf. Now, however, if Shuzen learned about his new skill...
'No, I must-'
"Speak, Kai. Were you standing by, watching my son die at the hands of the beast?"
The threat behind such an accusation was clear.
If Kai was weak, he would be killed. His only purpose in this new life was dead, so if he could offer nothing else...
'That's just how this world is, huh? I understand.' Kai thought just before he answered.
"No. When I heard that Est was in danger, I ran into the woods ready to lay down my life. Khazi was nowhere to be found at the time, presumably because he was searching for help. Either way, I was left to defend her. I had previous knowledge about the Juma, so I knew to take advantage of the lack of balance created by its feet. But uh, when I flipped it my ankle... sprained. Khazi did come in and try to help, but the Juma killed him. That- that slight opening is the only reason I killed the beast, Master."
Throughout his defense, Shuzen had done nothing but stare into Kai's eyes, not even paying attention to the apple he held in his hand, half-eaten. After Kai finished, he felt Shuzen's eyes boring into him, assessing not just his words but his very being.
Then Kai jumped, dropping the apple onto the floor-which became stained with blood as a result-as he clutched his left arm.
In an instant, Lord Shuzen had embedded his poison needle into Kai's arm and was now threatening Kai with a very deadly poison.
Lord Shuzen took his time as he approached the young elf, taking special care to relish in his fear.
Lowering his head so that he was at eye level with Kai, Lord Shuzen said slowly, methodically, "Boy, don't lie to me. Khazi had nothing to do with you killing the beast, and you know it. You- you unlocked a latent ability, didn't you?"
In a last-ditch effort to cling to a reality that no longer existed, Kai fervently shook his head, trying to discredit these dangerous affirmations.
"Don't LIE to me, boy! Do you think my son who had a C-rank fire ability would die to a beast, but someone who has no ability or taming specialty would defeat him? You think me for an idiot?!"
In a flash Lord Shuzen's hand slapped Kai's, leaving his cheek a red that shone through even blood. Kai met this slap and the continuous pain of the poison with little more than a glare.
He quickly softened his expression, knowing that hostility would endanger him and his mother, but it was already too late.
Lord Shuzen extracted the poison from Kai's arm, but it was not a benevolent gesture. Picking Kai up by his midsection, Lord Shuzen paid no mind to his fearful yelp as he threw Kai into the wall, even leaving a small dent.
Before Kai could even recover his vision after such a hit, Lord Shuzen was already in his face, now embedding his poison into Kai's neck.
Even without his injury, Kai wouldn't have even been able to breathe. As his vision turned murky and he struggled for breath, Kai was left unable to do anything but gasp for air.
After a few seconds of that pain, he suddenly felt all of it go away. Again, the poison was extracted, but this time it didn't lead to another attack. Instead, Lord Shuzen spoke slowly, deliberately.
"You unlocked a latent ability. Tell me what it is, or I'll kill you and tell your mom it was a monster. Or maybe you killed yourself. I'll have to see which I decide. The point is, she will only have me and little Est in her life at that point, you understand? Of course you do, you are smart after all. It would be a damn shame to lose whatever strength you have, but it would be nothing for me to make another heir. And this time, it wouldn't be some idiot halfwit I need a damn servant to train!"
Kai sighed in defeat as he felt Lord Shuzen's poison dance around his neck again.
In a low whisper, Kai said, "My power allows me to corrupt any beast. I- I don't know exactly how it works- I promise! But, without even defeating that beast my magic just... forced it to be tamed."
Lord Shuzen let loose a despicable smile at this revelation, the gears already turning in his head. Yes, he made a good decision not to kill Kai all these years.
He was going to conquer Kai's will, just as he had the beast.
Which would make him the ruler of everything.