
Has that been explained and i missed it??

Ofcccc in the novel (spoiler)
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So basically the city does experiments on fetuses in order to counter the virus. And the fetuses that survived all have something enhanced such as strength or intelligence, but have birth defects. These fetuses that have been Experimented on are called “mutants”.
Dr.seok and the 3 Majors in the immortal regiment are all “mutants”. One birth defect all mutants have is they all have something they are obsessed with. For Dr.Seok it’s rocks and for Major Yang I believe it’s trains. I don’t think Major Lee’s obsession was ever mentioned. Major Kwak was known as the perfect mutant cause he didn’t have an obsession and other things I’m not gonna spoil.
But yes, the obsession with rocks is caused by the birth defect of the experimentations.

If there is where do I read?

I finally found it https://chrysanthemumgarden.com/novel-tl/tts/tts-1-1/

What the fuck is this shit? Nevermind the crappy plot and how they treat the FL, I couldn't even read half the chapter bc of how bad the overlapping was.HOW HARD CAN IT BE TO FILL IT IN WITH WHITE THEN PUT THE ENGLISH TEXT OVER
Seriously. Why does such good art have to be wasted on a story like this.
I was literally gasped because what was that!! I was expecting that it would be building up for the side stories when they get together again and work it out but NO!! HE KILLED HIMSELF..