Havent read the main story (and don’t want to tbh) but do we have to read it? Is there a...

KML is not the main story, it only takes place in the same universe. Actually the author (she writes novels/webnovels) recently wrote on twitter that Grayson's story was the first one she came up with when she started to write omegaverse novels, which is chronologically the last one of the Millers. She is releasing it right now,~10 year later as the 4rth Miller novel out of 6.lol
KLM and KMIYC share the same universe, and there are some charaters which appear in both stories, it also takes place around the same time, but you don't need to read if you don't want to.
In KML we learn that Josh is Emma's (one of Keith Pittman's secretaries, he is the ml of KML) older omega brother, who works as a bodyguard and has a child. Emma has a crush on Yeonwoo, he is the mc of KML. Josh and Yeonwoo meet two times during the main story, he also sends Dane Stiker to help him.
Chase is an actor, he plays a role in one of the movies of Keith Pittman's production firm. He doesn't appear in KML, but they talk about him. Chase's older brother is Grayson's Miller, Keith Pittman's (best) friend. But as I mentioned before, the male members of the Miller family have/will have their own novels.

Josh also appears in the side stories, but there is a time skip so it is a few years after the main story ended.

Thank you sooo much for these details, honestly, even if i won’t read KML, i think these are important details. Thank you

As I said you don't need to read it. It's only a few additional informations you are missing out, but you don't need them to understand the story. The stories are really different, and I think more will like this one than KLM, because in KML the pairing is much more imbalanced and Yeonwoo suffers a lot.

sorry for camping in! seems like toru has read the novels, I just want to know how chase know about the child later? i havent had the chance to read the novel yet but im impatient to know

Chase is one of the more stupid extreme alphas, like Keith.^^
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He overhears that Josh has a child, pretty late in the novel, when they are already sleeping together. At that point he still thinks that Josh is a beta, although he saw the cesarean scar.:D
Since poor Chase only slept with one person (Joshua), he has no idea that Josh is an omega, which a normal alpha would have known during sex.^^

A short time later he sees the mark by chance, because Josh loses that ear communicator + plaster during a fight with his abductors. This is how he finds out that Josh is an omega.:D
He doesn't know that it is his mark.^^

By the way he is afraid that Josh gets back together with the childs other parent.^^
He is jealous of himself, like Keith was.XD
And he is willing to become a "stepfather", like Keith.^^

During the last chapter of the main story Josh brings Pete to a playdate. There is an dog inscidence, Chase is afraid of dogs, and Josh finally tells him that Pete is his son and that he was the omega who he slept with back then. The first thing Chase asked is, if he raped him, because he was afraid of that.
The story actually continues on the side stories.

Grayson is responsible of the dog trauma and other things, because Chase fell victim to Grayson's "helping"-problem (he was born an extreme alpha, so his problems with understanding emotions and right/wrong are no joke), but to "understand" Grayson you'll need to read his own novel, but you'll be in for some surprieses. He is the most hilarious alpha you're going to meet in the Zig's novels ( he is actually her first one). Most who wished him karma (because of Chase) started to like that weirdo and will now cry with him when he get's hurt (the webnovel is in process right now).lol

thats really interesting, where did you read the novel? i cant wait any longer for the manhwas updates

nvm i found it :]

"The first thing Chase asked is, if he raped him-" your honor, thats a whole green flag right there, tysm for the spoilers

lmao i want grayson's story right this instant, hoping we'll have his manhwa adaptation too