(sorry, some of these may not be 100% accurate as I have forgotten some terms) Okay so iirc
Ml's mom - is actually a spirit(or someone special???) of some sort. She's so nice blah blah, and it catches the eye of another spirit. This spirit falls inlove with the mom, cuz of how she's literally so freaking nice and kind. Another thing is, the mom is able to see other beings(like how the ml can see ghosts/spirits such as the fl!)
Ml's dad - A duke. He never cheated on his wife, the duchess. He actually died from the war(deliberately done by the duchess and her lover). So you wonder, why is he alive? Cuz it's actually the spirit who fell in love with the mom who is residing in the body! And another question is, if he so loves the mom, why can't he defend or take care of the ml properly? Well it's cuz spirits can't interfere with the human world. One time something happens and the ml begs for help, the duke broke the rule and he bled so bad, he had to hide in his bedchambers.
Duchess - she's evil through and through. You'd think she loves her sons? Nope, she loves herself more than anything. She has 2 sons, the first one is the duke's biological son, and the other son (axel iirc), is actually her lover's biological son. She favors her first son more than the other, despite him being dumber and more foolish. It's literally just cuz he got the duke's blood running in him lol Later the first son realizes that the duchess doesn't give a f about him and betrays her. The second son also betrays her mom and sides with the ml. When he was young, he kept wondering why his mom kept favoring his foolish brother and he later found out the truth. Though he did bully the ml and is aware that he isn't innocent, so he told the ml that it's okay for him to be exiled and basically live peacefully outside the duke household.
Ml - can see spirits just like his mom, but pretends like he can't so they wouldn't call him crazy just like how they treated his mom. Extremely loyal and faithful to the mc.
Heroine - she's fake, entitled, and can't accept that ppl don't like her. She falls immediately for the ml when she first saw him. Ml doesn't give a flying f about her tho. She legit keeps pestering the ml soooo many times, making up excuses thinking the ml is just playing hard to get lol finally, the last time she ever chased for the ml the fl was there. The fl was straightforward and told her how she's literally like a stalker chasing for the ml, and not the other way around.
Fl - she actually dies, burned by the duchess's first son. Actually, before this the duchess and her sons realizes that the ml's weakness is the monster inside the closet. The duchess uses it against him, and basically holds the fl hostage. Fl gets killed while the ml is away to basically somewhere for kids who r troublemakers(cuz he fought the duchess who was trying to take/hurt the closet.) The stupid first son gets excited and sends a letter saying that he killed the fl and even sent him some ashes. Ml goes COOOCOOOO... The duchess is not happy with what his son did, since she wanted to keep playing with the ml(that's how evil she is). Dw tho, fl gets basically revived by the spirits, and she even meets the second ml there lol
Also, the ml almost killed himself after finding out the fl died. But he basically woke up and decided for vengeance. When he comes back(he's an adult now, like 21??), he basically meets the duchess and the first son at the ball hosted by the empress. The duchess gets scared SHITLESS. She has always been intimated by the ml cuz of how he strikingly looks exactly like the duke. The first son?? Oh his inferiority complex got more bad. He literally just wasted his life by drinking, gambling and playing with women. The stark difference between him and the ml rlly damage him lol

Another shitty dad that's gonna get excused and forgiven. Blurghhh