I 100% agree with every single word you said. 
People are so mad at him for wanting to see his grandma and it doesn’t make sense to me. But he definitely shouldn’t do it behind his mother’s back and he definitely is mature enough something happened between them so there’s a reason they’re not in touch.
Honestly Dojin is the one to blame here                                            
                                                He must know something happened, he knows his mom doesn't want to have contact with her, but maybe he's reaching out to grandma first because he's trying to understand her? She's good to Byul, so it must puzzled him why in God's name she left his son in that place. It's so difficult to simpathize with her, for readers she was selfish and a monster but also a victim, but for Byul, she's just his grandma. I hope he gets to learn the whole true from both sizes and be the bridge for healing. At least for Hyesung because the sole mention of his mom, rightfully, makes him sick and outburst in anger. But probably because he also felt hurt of the lies and hiding, and a sense of betrayal at Byul's actions and words defending his grandma and making comparisons between them.
It's easy to talk when one is ignorant and inmature.
Love how all the comments agree that Dojin has all the blame                                             
                                                She's good to Byul, so it must puzzled him IF HE KNEW why in God's name she left his son in that place.*
Also, Byul feelings also come from a place where he feels that he was never wanted at some point and even if he loves his sibling and they are pretty much showered with love, the sibling was wanted since day 1 and that memory from such young and impressionable age must still hurt him deeply.                                            
                                                It’s his decision to make not yours and not his parents’, under their watch. especially when you’re talking about a sane person that doesn’t harm him and isn’t abusive towards him.
(Hyesung being worried about it makes sense, but reality is different)
And every decision he makes is legitimate, whether you or they like it or not.
She is still his grandma, regardless of what she has done, And it’s his decision to make if he sees her as his grandma or not.
It has nothing to do with his mother, he shouldn’t be put in the middle of this, children shouldn’t be part of family drama to begin with and be forbidden to see a family member. Him wanting to see his grandma is only natural.
If Hyesung would tell him to not see him I think it would be a really bad decision and as a parent I wouldn’t do such a thing. There is a solution to this situation
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                                                I they talk about it openly, And it makes me wonder if it hurts him to know his mother abundant him when he was younger because he clearly does not remember it. He was also showered with love since day, one by his own father and uncle Heeso. So I don’t think he was not loved or anything like that but maybe because they mention it it hurts him 
And I think it’s beyond that, It’s the feeling he got also in The career he aimed for and got kicked out… 
Going to his grandma it doesn’t have to be anything he is not, He’s just talking to her, Existing without any expectations And just being loved for who he is                                            
                                                Definitely! I also think that Hyesung doesn’t have to have any connection to her,
But if Byul Would’ve talked about it and asked about it. Maybe they could’ve found another solution. Like him going with Dojin.
Meeting her only outside, for example. Anything that will make his mother at ease…
I’m really looking forward to see how it’s going to unfold, And I hope Hyesung will slap Dojin lmao                                            
                                                Yes, I agree, but this story in particular is about generational trauma so it's gonna be all about the moms and what they did o didn't do  Byul is hurt because it was his own mom, the one that he loves so much and is always on his side, tried to abort him and later disappeared from his life when he was an baby infant and after a while came back. He only knows that part and little bits that Dojin surely told him from his pov but he needs to know the whole true. I think it's because he's innocent too that he thought he could have a relationship with his grandma without his mom knowledge and consent and everything would be fine... 
He just want to know his grandma, have a relationship and understand what happened but the way he did it was not the best. He loves his mom and his family but it's not wrong for a child to seek answers in every place he can get them.
The fault is in Dojin that didn't communicate this to Hyesung and find a solution. He's the father, the husband, the partner and till this day he keeps messing it up.
And, even if the grandma is trash, one can still get to know her and don't forgive her for her actions. The thing is that Hyesung needs to heal, he doesn't need her in his life but he needs to make peace with his past and the thought of her.
But again, having Dojin keeping his and his son's secrets is bad parenting. He must have a very good excuse I hope...
Byul loves his mom very much, he was so regretful to have yelled and hurt him. He was raised so well in that aspect and he just want to fill that part of himself that he doesn't know how to do it alone without upsetting everyone. But I don't believe he's mentally prepared and he will need Siwoo's help to understand his whole family drama.                                            
                                                I really do think that it’s good. He is innocent to some extent. It just means you did not have to leave like his mother did and he has so much more opportunities in a better life than him. 
That’s why it frustrates me when people say you should not meet his grandma, Because he was born out of rape, and it was unwanted. But it’s not his fault and I think it’s so toxic to think Hyesung needs To see him or behave in a certain way because of this.
Byul is sooooo pure my Shayla, And having the feeling of being abundant But still staying With your mother does not align with the abundant his mother went through, Their traumas are different And it’s hard to understand that.
You’re so right I love him so much and he deserves the world and I hope it would be happy with Siwoooooo I Feel like I raised him like seriously he’s so my babyyyy. And hearing those things about yourself when you are a child is honestly so wrong and I wish they would’ve thought about it more before talking about it when he’s at home… No child should live with the feeling of being a burden and a mistake.                                            

		
I can understand Byul. He's young, spoiled, almost sheltered but he's also very ignorant and carries a deep wound from feeling unwanted even if he's so loved by his mom (and dad) and friends. He can make mistakes, but can also grow up and learn. All he needs to do is talk with his mom in a more calmer way and try to reach for understanding. Mom also looked at his phone, which was bad, but keeping the secret is worse. Byul has the right to meet his grandma, even if she's a piece of shit, that's all on him. But keeping the secret meetings is worse. But, it can be fixed because there's foundation of love.
BUT Dojin... no. Never forget and forgive what he did. He's a better person now but he's so unlikeable... let's see how this goes.
AND
They kissed. I've never been a fan of "kissing your crush to stopping him from crying and calm him down", but it worked. Byul's mind went blank.