After the death of his adoptive father, he suffered from bipolar disorder and he was bad-tempered and out of control. It was much more serious than how he was now.
When his condition acted up, he had hurt Xue'er several times.
But she stayed with him and did not give up, even though he had almost killed her a few times.
From her, he had always felt a long-lost warmth and care. She was like his sister, his closest relative.
But one day, she suddenly confessed her feelings to him.
She said that she liked him.
At that time, he had no experience in love and did not know how it was to like someone.
Was that warmth he felt from her this thing you called 'like'?
He did not want to see her sad and disappointed, and so, they started to date.
After they got together, he went to Country S so that Grandma and Xue'er would have a good life.