
But I can’t grasp what’s happening Σ(っ°Д °;)っ since Shuli found the letter ion understand a thing anymore and even thought that Shuli’s husband is gay and stuff ┗( T﹏T )┛heLP

The count's the previous wife sibling, the children uncle. They exchanged letters because they were friends, and he sent a letter explaining that he didn't had a sexual relationship with Shuli (as he's deep in love with his previous wife) and wanted the count and his mother knowing that.
Shuli'll use the letter as proof that they never consumed their marriage, and because of that she'll demand a divorce. This'll make the first son the family head and he won't lose his hand or even his head as punishment.
So Jinwoo is the next shadow monarch. He will be their next King no? (๑•ㅂ•)و✧ I’m so excited damn!!!
Well yes, but actually no
Is it ike reincarnation? Transmigration, but he forgot? He was always the Shadow Monarch, but he forgot that he was? What is it? Or maybe it's none of it.
It's more on like inheritance actually. Also, the original shadow monarch was said to resemble Jiwon in the novel.