This completely my opinion

It’s not as simple as it looks—the situation is far more complicated. Both siblings lost their parents at such a young age, and that left deep scars. The brother, especially, grew emotionally dependent on his sister. When you lose that kind of parental love too early, you start clinging to the closest person you have—and for him, that was his sister.
On top of that, the younger sibling carried an enormous need for affection, a desperate expectation of love from everyone around him. But his pain didn’t stop there—he was also SA’d by his cousin. For a child, that kind of trauma doesn’t just fade away with time. Some wounds never heal; they shape the way you grow, the way you trust, the way you see yourself and the world. Unless someone has lived through it, they’ll never truly understand how deeply it breaks a person inside.
I’ve worked in an NGO for years, dealing with children who went through similar things, and believe me, sometimes the pain is far worse than what we can even imagine.
Coming back to this story—his sister had no idea what he was going through. I don’t blame her for it, because she herself was still young, trying to survive her own battles. But for him, all of that silence, all of that loneliness, kept piling up. It was like a storm building inside him. So when he asked her to attend that parent meeting, it wasn’t just a small request. It was a trigger. In his head, it echoed as: “Why didn’t you notice me? Why didn’t you care? Why did I have to suffer alone? If I had parents, would I have gone through all of this?”
And then he snapped. Not because he hated her, but because he loved her so much that her absence, her unawareness, cut him the deepest. To make it worse, in a society like Korea where bullying is rampant, he was probably already being ridiculed for not having parents—which is why he wanted her to show up at that meeting, just to feel like he wasn’t completely alone.
Now, I’m not excusing the words he said, but I’m sure he didn’t truly mean them. He was drowning in pain, suffocating under everything he had been carrying for years, and that one moment was when it all burst out. Sometimes, the people we lash out at the most are the very ones we love the most—because deep down, they’re the ones we desperately wanted to notice our silent cries.