
Jiwook has some serious mental issues. Σ(っ°Д °;)っ
And surprisingly shitty parents. Why would you constantly compare your children (Twins! Even worse!) and allow/encourage other people to do the same?! That is a recipe for disaster! So far, Han Siwon seems like a good person, although a pretty dense one - which made him a lousy brother.
I wonder how they got to what we saw in chapter 1. Did Jiwook promise something to Joohoon in exchange for breaking Siwon? And what could that be? And how did Woojin end up in the twins' house? He seems to hate everyone in their school, so how did Jiwook manage to get that close? Maybe a school project?
Oh! And it looks like the "identity theft" theory might be wrong. :(

Yeah, the twins theory died. But I still hope that Jiwook dies and SiWon comes back to take his body. It likely won't happen, but I can dream.
And SiWon was naive, not dense. He never understood why his brother pulled away because his brother NEVER Talked to him. More than once we see him reach out to Jiwook and Jiwook just slaps his affection and concern away.
Take a look at all the stories where people did not know what was going on with siblings or children. Children hide stuff from parents--sex, drugs, drinking, bullying, etc. So, as long as they put up a nice front (as we saw Taemin-SiWon and Jiwook do in front of mom and dad), parents like to think everything is fine. So, I wouldn't say they were shitty, I'd say they were not observant or even very wise.
TAemin's parents were shitty.

No their parents are not shitty. Jiwook is. He is a double-faced bastard who act all nice and smiling in front of their parent but act differently toward siwon in private. Just reread tge earlier chapters. No wonder their parent did not notice that

I don't think you will want to admit your parents are wrong with the way they grow you up. most kids that go though abuse won't admit it, and in this cause you can see it in Fox thoughs. he never did blame them for not loving him like his brother.
and he did have mantel isseas that start cause of them.
but okay, you support in prefer a brother over the other, good for you anon.. ┑( ̄Д  ̄)┍

Where do you see that they did not love him? Show me? Because accepting praise for a son who is doing exceptional is not NOT loving the other one.
That is not abuse. Abuse would be if they said, "Oh, that other son is a worthless crap who doesn't try harder."
And it's normal to prefer a kind, caring person to a malevolent, vicious bully. Or do you love vicious bullies in real life, too?

People at the party were commending SiWon. They were not abusing Jiwook. (The faded dialogue was in Jiwook's head, poeple weren't saying that.) Which makes sense, because if someone gets an award, you congratulate the person who gets an award.
Is it WISER and KINDER to say nice things to both, sure. But generally, if soeone has 4 kids and one kid gets a scholarship or wins a track meet or wins an art contest, that's what poeple will mention and compliment.
That does not equal abuse, unless one has a VERY liberal definition of abuse, which comes down as an insult to people really abused, like Taemin and young SiWoon.
Again, show me where a scene where the parents ignore or put down Jiwook in favor of Siwon or are mean to Jiwook. Because I don't see it. I see party talk, not years of parental neglect.

I meant dense in the sense that he didn't realize that his brother was bothered by the constant comparing. I say this by personal experience. My parents used to compare me and my brother in an attempt to make the other try harder, and it took me a while to figure out how to make my brother not resent me for it (I'm the eldest). But I did notice that it was tearing us apart at a pretty young age. Siwon didn't. Which is why I'm saying he might be a bit dense. It was clear that Jiwook was also hurt by the fact that Siwon had no idea what the problem was, just knew that something was wrong.
The parents not noticing the consequences is indeed not surprising, Jiwook is a good actor. And yeah, we have yet to see any good example of parenting in this story. ╮( ̄▽ ̄)╭

Even though I agree that we have yet to see any proof of Siwon and Jiwook 's parents favouring one child over the other, I have to say that there are signs of parental neglect there. It is difficult to spot problems if the child is hiding it and brushing it off, but my first impression of them was that they're certainly not good parents. In the early chapters, Taemin (in Siwon's body) just got home from the hospital and seemed hesitant to go to school. Jiwook told them that he might have been bullied and that was why he didn't want to go back to school. I remember thinking to myself, okay, your son just survived an incident which could've been a suicide attempt, his brother said it might be because he was bullied at school, now he lost his memory and you're just gonna let him go to school without questioning any further, talking to the teachers, or trying to figure out who he'd been hanging out with and if he'd really been bullied? Also there are some of Jiwook's behavioural changes that are easy to recognize (dying his hair, smoking, hanging out with bad crowds) and it is undeniable that the parents should've noticed there was something troubling him if they'd paid some attention.

PICTURES FROM THE RAWS OF THEIR THEIR HUMAN FORMS! (╯°Д °)╯╧╧
https://uploads.disquscdn.com/images/2e3450afb25093163e750e6698f37b1c867e251e022a22a7bff031dd415cfc41.jpg
https://uploads.disquscdn.com/images/72a080624ea0cfc85a9a9aecf84e130072494765145ed801e047a6ca006fc88e.jpg
Someone posted this in another manga reading site and wanted to share with you, in case you hadn't seen it yet.

Name list:
Dog: Sousuke
Rooster: Akebono
Boar: Kusunoki
Rat: Nakayoshi
Bull: Kaede
Tiger: Yoshihiro
Dragon: Kouetsu
Rabbit: Mikoto
Other four missing. Thanks for this! ^^

About the issue of Kotarou's family:
So normally the head of the main family, the one being possessed by Koma, must have a child, who will continue the family's duties. But being possessed by Koma lowers their fertility rate so sometimes they are 100% infertile and have to resource to sex with someone of the same sex in order to pass on some spiritual power. And that lover must have a child in order to continue the lineage.
How did they managed to keep it in the family for so long? Adult adoption? Incest? And how the hell is there even a branch family if they have so few children? Btw, Kotarou is very lucky to be born gay considering his circumstances. And why does their partner must be of the same gender as them? Is it about the penetration? The boar did say he would seed Nogi to give him power. But that would mean Nogi would have to bottom for Kotarou and that was not the image I got from that conversation about Kotarou being cute.
I'm confused.

According to this page the only people in the Komano family to not be fertile (no viable sperm) was the first generation head and kotarou so far.
http://www.mangago.zone/read-manga/eto_irokoi_zoushi/mi/06bda3bbe9069465bcef0a2204df9b80_chapter-3/22/

Did Nogi set fire to the family's main branch's shrine?
He has a motive: forcing Kotarou's hand and making him accept Nogi's (disgusting) proposal. Btw, this is probably the only context in which I'm almost ok with someone being raped. He was willing to force a boy to sleep with him for spiritual power, so why wouldn't he be ok with getting fucked if it gave him some power? I agree with the author: karma is going to come back and bite you in the ass.
Does that mean that there is a modern Jun as well? I don't think Jun went back to his world. He died, so it's not like there is anything to return to. He is probably just lost and hiding from the rain somewhere. But this opens a possibility to a love triangle: ancient!Jun X modern!Myung X modern!Jun XD
*Shiwoo, not Myung