Alex who proclaimed that, Lilitth must die first to live, was simply saying the same line as his dad. He wasn't truly planning to kill Lilitth, quite the opposite he was truly planning to save her. Though he was indeed planning to hurt her until she loses consciousness.
Alex who was full of fighting spirit, started to finally truly think of a way to make the loli he was fighting fall unconscious. The things he understood, as he fought the girl was limited, but he was sure that clue lay hidden within that limited information.
The first thing he noticed was obviously her physical capabilities, which go beyond what a human can do. Yet even with her enhance abilities, she still wasn't able to kill Alex simply because she was fighting like a wild animal.
The next thing he noticed was her skin, muscles and most probably even her bones were harder than metal. Way harder than the knife Alex was using, since it shattered.
'Still those are strengths, not weaknesses, there must be something I'm missing.' While Alex was thinking of ways to make Lilitth faint, her attacks which slow down came back to the usual pace. When Alex saw Lilitth up close, a sudden realization had dawn to him.
Lilitth might be a super artificial human, but in the end she was still within the realm of a being human. That would mean she still suffers the same weaknesses as a human does. She needs to eat, she needs to sleep, even though her body regenerates like crazy, she still bled. She still had the same body parts a human had.
That would mean Alex just needed to shake that brain of hers, since no matter how strong her outer body was, her insides should still be the same as a normal human. Alex was not sure if the people in this research facility, had made Lilitth's insides as strong as her outer body. Still this was the only plan Alex could think off at the moment, so it was the worth the gamble.
He just needed her to stay unconscious for a few seconds, so that he can find that chip implanted in her, the way the electronic voice explained about the chip, made Alex feel like it was somewhere on her body, not inside it.
Still if it was inside it might be harder, but he would still try to save her. Alex's motivation to save Lilitth was growing stronger. Since it felt like, if he saves her, it might lessen his burden, he might feel that a bit of sins will be forgiven, as if he had saved himself.
Alex increased the rate in his use of RELEASE, he felt his body screaming, but this was the only way to save the child in front of him, so he didn't mind the pain, nor did he care about the future damage this might give. All that matters to Alex was the here and now, what matters to him at this very moment, was that a little child was asking for salvation, same as the him back then. So no matter what, he must give this child a chance to gain that salvation.
Alex released the latent power of his body, he felt an overwhelming rush flow through his entire body. Without delay Alex burst forth, only aiming at Lilitth's head, and chin. Though his attacks would have killed a normal person, Lilitt was unscathed. Yet because of Alex's strong continuous attacks, she couldn't move.
...
Lilitth who heard what the kind Onii-san said was bewildered at first, but then she smiled a bit sadly in her mind. 'So in the end, the only solution was death.'
When Lilitth heard Alex say the words she must die first in order to live and be free, she thought he meant it literally. That only in death can she be reborn, so the slight hope that she held, finally shattered. Still she was truly grateful to the Onii-san, since he was about to relieve her from her suffering.
She was lucky enough to meet such a kind Onii-san in the end. Finally the hesitation in the Onii-san's attacks were gone. He was finally showing his true skills, the speed, and strength of his attacks, were extremely different from what he had shown before.
Not only that, he was concentrating all his attacks on Lilitth's head. It was very obvious that he wanted to end this quickly. Lilitth who wasn't in control of her body, knew that right now, at this moment, even if she had control, she wouldn't be able to escape this torrent of attacks.
The attacks were heavy, but they didn't really hurt, but she somehow felt the damage piling up. She felt weird, it was a different kind of sensation. The only way she can explain the feeling, was it was like she was floating. Those were the only words she can think of that can describe the current sensation she was feeling.
It was finally coming, the ending she so desired, her consciousness was slowly fading. She was just a bit sad, that she wouldn't be able to meet this kind Onii-san anymore. Yet the moment before she lost consciousness. He heard the Onii-san's final words, which confused her.
"From this day forth you are the daughter of Carlo Samarita, and the little sister of Alexander Samarita, from today onwards you are Lilitth Samarita." Those were the final words Lilitth heard before losing consciousness.