LWJ's BITCHen

The side character im trying to find is part of one of those cliche romance transmigration webtoons. Im pretty sure it was a "trasmigrated as the daughter of the emperor" situation...
I have this distinct memory of a "female duke" character who maybe had red eyes but almost definetly had long black hair. She was strong and fought with a sword (though i dont know if we ever actually saw her fight), her territory was probably bordering another kingdom or a monster region or sumt and was "quite far away from the capital".
The reason she "picked" that territory -and the most distinct part of all of this- is because she had a brother/nephew (a teenager boy with short black hair and amber eyes maybe?) who was "sick" (actually it was a curse). And because either him or both of them are related to the "dad emperor" guy she chose to stay away from him to not seem like a threat and become his target.
I think the mc meets the teenager brother in the "palace garden" or some cliche like that and becomes his first friend. Thats how she is able to convince the "cool female duke lady" to talk with her "dad emperor" and get his help in saving her brother/nephew.
Does anyone know which Manhwa/Webtoon has this subplot?

I read it a long time ago and it goes like this (i think): the mc's dad was a mafia boss but he was murdered. The mc is in highschool and good at fighting smh and he's mom is very badass but she decided to raise him alone to separe the guy from the mafia shit. And then like, halfway through, the protagonist changes and is now this bald(maybe?) Guy that trained under the same master as the previous mc's mother (not sure about that doe). And now the original mc is kinda the antagonist cause he wants to acenge his dad??

Also, i could SWEAR this was named "God Of Highschool" (i read it before "The God of Highschool" got famous/i knew of it so im not mistaking them both).
I don't even wanna read it at this point im just desperate to confirm this isn't a fever dream pls help :,)