Okay, allow me explain the "cult" scene.

As the 2FL said, "I am only a mouthpiece". It hints that she exists because it humanity has been secretly desiring to see who slept with whom.

Later, she also said that her existence was exactly to bring in the S-Day, and after that it doesn't matter if she dies or live.

The "cult" is the representation of her power. She gains power because there are people being controlled by the S-glasses. The secret desire of those people is giving her power.

This is a common trope even in European mythologies. The trope goes that the g-ds exist and have power because humanity secretly desired to have g-ds. The more a g-d is worshipped, the more powerful that g-d becomes.

In Neil Gaiman's "American Gods", he deeply explored this ancient trope and adapted it into the modern world. In his story, there is a g-d of handyphone. The more people use it and are glued to it, the mire powerful he becomes. And the many, not all, of the old gods are weaker, dying, or getting murdered because they no longer have worshippers and thus almost powerless, not even to protect themselves.

In Neil Gaiman's "Sandman", that same ancient trope was used again. You can watch, I think it was in S01, the episode where a goddess died because she's so weak. She had few temples left and few worshippers. Guess what her temples are? R-21 adult bars. Who were her worshippers? Patrons of those bars.

Even in Greek, Roman, Egyptian, and Nordic mythologies, this trope was touched on, and sometimes used to weaken another g-d.

Going back, that is what that "cult" is about, and potentially that is what the 2FL's identity is. She is a goddess made out of human desires and to power up she need constant worshippers.

Noticed how she tried to lure the detective? Because the detective did not fall under her control. Meaning, the human wearing the S-glasses should unleash their inner desire to murder, to accuse. But the detective remained objective and in full control of himself.

Later, after she died, she appeared as a spirit to the 1FL. It's a hind that the reaction of humanity during the 1 year time jump, enabled her to exist as a spirit, and started following the 1FL. Now, she truly is a goddess, no longer one trapped in a shell that dies.

I hope that helped.

The more I think about it, the more it becomes deeper.

Let's push this analysis/interpretation further:

If the 2FL is the avatar/g-d/manifestation of humanity's desire to see who slept with whom.

The 1FL is the representation of humanity's "good" side and is fighting that g-d.

Ancient mythologies are filled with mortals vs gods. In S-Line, we have the 1FL fighting for the "good" side of humanity. While the 2FL is humanity's desire for revenge, accusations, and murder.

Unfortunately, the 2FL won the first round. Which is often the case, the gods win the first round. Humanity is pushed back. New rules and laws imposed on humanity.

Remember the 1 year time jump? As the 1FL narrated, it was chaotic. It took the world a year to settle down. What's the best way to do it? New rules and new laws.

First round: the 2FL, the goddess/manifestation of humanity's desire to see who slept with whom so they can exact revenge, murder, accusations, blackmail, wins.

But the 1FL lived. Which could mean there is still hope.

And there is hope. The 2FL might have achieved goddess status (since turning into a spirit) but humanity hasn't broken down to chaos and anarchy.

The 1FL survived and so does humanity's inherent desire to do "good". Humanity learned live with it and decided to return to ther daily routine.

No doubt, scientists are finding ways to "turn-off" the S-Line.

And they'll need the 1FL.

It's a modern take on mortal vs gods. Or, good vs evil.

Another take is this.

The 2FL was Pandora.

The 1FL is the box.

The 2FL opened the box and let loose the ability to see the S-Line. Now humanity has to live with it. Just how humanity learned to live with sickness, diseases, and death because the original Pandora let loose the curses.

And just like how there is Hope in the box in the Pandora's Box mythology, there is Hope in S-Line—the 1FL who miraculously lived.

That's an interesting take..I had no idea how Gods were used in European mythology. 

But it was the Director job to make us understand than giving such vague E6. At one point I thought it was all a dream and FL is in a psychiatric ward  then thought its a parallel world..It was messy execution wise leaving people to interpret in their way..

To begin with they didn't explain why  FL was born with the ability to see S-Line..Like was she  randomly chosen or what? And it took away the uniqueness when everyone started using the so called glass..

Concept-wise creative  but they didn't develop it properly..

I second the Pandora's box analogy. I think the glasses represented humanities obsessive curiosity. Everyone who put them on went insane in some way or other. If I am not wrong, the source webtoon/manhwa takes place in the post-apocalyptic society where everyone can see S-Lines. Maybe this serves a prequel...

The entire series was nihilistic. But 1FL rejected the meaning that was forced upon her. Resembling that of Evangelion. And in a way, the ending basically followed the footsteps of NGE.

 Ame_iro_hito:

I second the Pandora's box analogy. I think the glasses represented humanities obsessive curiosity. Everyone who put them on went insane in some way or other. If I am not wrong, the source webtoon/manhwa takes place in the post-apocalyptic society where everyone can see S-Lines. Maybe this serves a prequel...

The entire series was nihilistic. But 1FL rejected the meaning that was forced upon her. Resembling that of Evangelion. And in a way, the ending basically followed the footsteps of NGE.

Ooh, yes, Evangelion! That was excellent! You're right.

 Poongs:

That's an interesting take..I had no idea how Gods were used in European mythology. 

But it was the Director job to make us understand than giving such vague E6. At one point I thought it was all a dream and FL is in a psychiatric ward  then thought its a parallel world..It was messy execution wise leaving people to interpret in their way..

To begin with they didn't explain why  FL was born with the ability to see S-Line..Like was she  randomly chosen or what? And it took away the uniqueness when everyone started using the so called glass..

Concept-wise creative  but they didn't develop it properly..

I agree. There were so many things left to the audience's interpretation or expecting the audience to connect the dots and fill in the blanks.

Though, I kept reading that it was a prequel to the webtoon and manhwa. If so, it could explain why it was written this way. I mean, I've read prequel literature written this way before but it was meant to be read after reading the original. In this case, they should've made the main storyline first before the prequel.

Agree on prequel..Usually they are written after the original..Week Hero Class was done well tho..Many loved S1 (prequel) the most compared to S2..

Lol, Concept of S line and FL that can see  S line, Glasses that enable a person to see S line was already fantasy category. from first 5 episode  people already know or had inkling about SFL is the one that is distributing glasses and even control S line .

Don't know why people have difficulty in digesting that SFL was more than human.

I like your explanation as it shows the depth of the story. I only wish the writers themselves expanded on it within the drama. It would have made for a more compelling and comprehensive series. Nevertheless, kudos to them for making something unique in a very unoriginal and repetitive industry scape.