Necessary Infodump (ahem, cough cough, don't mind me)

"Is anyone there?"

Immediately, Liao Guiren heard a slight ping sound, followed by a cold sounding feminine voice saying the following:

[Hello, host. I am here.]

Startled, Liao Guiren asked, "Who are you? And why are you calling me host? Are you like a parasite or something?"

[I am a system, host. Model A12-Beta-Y209 to be exact. I am calling you host because you are my host, and I am existing as an entity bound to your consciousness and life. So long as you don't die, I am now unable to separate myself from you.]

"Model A12-what? What does that mean? And can you tell me what's going on? That guy who was just here, where did he go? And how are you doing this anyway? Speaking in my head? And-", Liao Guiren was cutoff before he finished.

[Host, my model number is exactly that, a model number. I am part of a series of beings similar to myself who all serve the same generic purpose. As for how I am doing this, you don't need to know that right now. It will become clear to you later in your life. The individual from earlier has been forcefully teleported to the USA from China, where we are now.]

Still very confused, Liao Guiren managed to grasp the key point.

"Wait, what do you mean he's in the USA? So he's not dead?! What if he comes after me?"

[I will forcefully teleport him away again host. Although I should advise you that if I do that too much, he will learn not to kill you, and I will not interfere with anything he does that is short of murdering you, host, so it's recommended that you don't let him get close to you like that again.]

"...So I'm in a race for time now? Until he comes and finds me?"

[Yes, host, that is an accurate summary of your present circumstance.]

Calming down a little, Liao Guiren started to think. Which didn't actually do much at the moment, but he did calm down. After having done so, he thought of a few new questions.

"Who created you? And why did you help me? How powerful are you?", he asked.

[Knowledge of my creator is classified. I am powerful enough to fend off any mortal threat, host. As for why I helped you, it is to fulfill my mission.]

Hearing the system say that it was powerful enough to fend of any mortal threat, Liao Guiren was half amused and half afraid about what if it was true. Nonetheless, he steeled himself and continued asking another question.

"What is your mission?"

[To help my host achieve immortality, following which I am to serve as his slave thereafter for eternity, should he desire it. My creator said he thought it was romantic to be enslaved to the being I was made to help achieve ascension all my life.]

"Why does you creator care about making me immortal?"

[Apparently, it's because, and I quote: "Immortality is so boring, ugh, and anyways, the more the merrier, so why not have a few random immortals pop up here and there." Following which, it is said that my creator launched a project to create a series of beings to assist in the immortalization process, of which me and my fellow systems are a part of. I can not disclose any further information, host.]

"..."

Why does this creator fellow sound kind of bizarre? Anyways, that was none of his business. After having his most pertinent questions addressed, and having a bit more of a grasp on his situation, he pondered. The system spoke of immortality as if it was no big deal, but he doubted it would be that simple. 

He asked, "Can I refuse?", to which the system replied:

[Yes. But the man from earlier will ruin your life.]

"I thought you said you wouldn't let him kill me?"

[Yes, that is correct. I will, however, not stop him from making your life a living hell in the meantime. Although I don't know quite why he would do that but who knows. Maybe he'll torture you to find out information about me, and how I'm teleporting him, or maybe he'll cut you up just enough to not kill you so that he can piece by piece dissect you to try and find what's in you that's stopping him from killing you.]

Hearing the system's gruesome words that it (she?) said without a hint of emotion, Liao Guiren felt a pang of dread run down his spine and he hurriedly asked, "What should I do?! Also, are you a she or an it?" 

[I am asexual host. I have a feminine voice because my creator liked it. You can call me what you wish. As for what to do, I would recommend becoming strong enough to not have to worry about weaklings like the man from earlier anymore.]

Weak?! So that was weak to the system, huh? Well, it did manage to forcefully teleport him, so one could guess it was much stronger that him. Plus, it did say it could "fend off any mortal threat". 

Liao Guiren still hadn't really come to terms with what was happening, but he suspended his disbelief and asked, "How do I do that? Also, why choose me as your host?"

[You can get stronger by cultivating host. I can give you a basic manual to follow, that also has basic information inside it about cultivation, since I'm sure you know not even the basics, including what cultivation even is, but the rest will be up to you. I would recommend reading it as soon as possible and then hiding it away somewhere, or even burning it if you can manage to memorize it.

As for choosing you to be my host, after running a sophisticated multiverse simulation, you were the most likely candidate to be able to achieve immortalization that I could find, for a variety of entirely coincidental reasons. Don't prove me wrong, host.]

Liao Guiren wasn't exactly satisfied with the system's answer that he was the essentially chosen due to pure chance and luck based on some simulation, but there was nothing he could do about it anyhow. It had already happened, and if it hadn't, he would be dead right now. He proceeded to ask the system for the so called cultivation manual while slowly getting up off the ground, following which a red leather-bound book appeared in front of him with the words "Sun and Moon Golden Technique" written on the front, and the word "grimoire" printed in tiny letters on the side.

Before opening it, he asked, "System, what does 'grimoire' mean?"

[A grimoire is a book that's been enhanced using spatial manipulation to store more pages than are shown at any one point in time. Of course, it doesn't have to have more pages than are visible, it's just that it can have them if need be. Grimoires can also store energy that they can use to create pages. There are also other potential capabilities they can have, but you won't see those types of grimoires until you become immortal, host.]

"Then, how many pages are in this grimoire?", Liao Guiren asked excitedly. Yes, excitedly. He was excited to be a part of this type of fantastical scenario. It was finally fully dawning on him that his life was about to be very, very different, and he was afraid, certainly, but also very excited.

[Open it and flip to the last page to find out, host. The page number is at the bottom.]

Liao Guiren did so, and he was astounded to find that the pages just kept on going, on and on. When the previous pages needed to go away to make room for new pages, they would fade away into the inside of the front cover, and more pages would appear out of the inside of the back cover.

The pages must have fallen for a full 30 seconds before stopping, and the number at the bottom of the last page was the following:

'3049'

There were 3049 pages in this manual!

Liao Guiren was somewhat dreading reading it all, but the system chimed in and said:

[Host, not all pages have to be read at once to gain power. Only the first several hundred pages are needed to begin cultivation and gain enough power to protect yourself against your current enemy, Gao Zian.]

The system said it as if a few hundred pages were only a little, but then again, if these are the kinds of books the system is used to reading, then maybe it really was just a little for it. Anyways, he had to hurry up and read, and start 'cultivating', whatever that meant, as soon as possible, because who knows when Gao Zian might come back, and what he might do when he did.

Closing the [Sun and Moon Golden Technique] for now, Liao Guiren kept it close to his chest and walked back to his apartment wearily, keeping an eye out on his surroundings. When he finally got back home, he collapsed on his bed, grimoire still in hand, and went to sleep.