The boy who has been secretly in love for four years is going to emigrate ... what should I do?

Ask him if he likes you because you like him so much. In fact, I think he likes you, but the reality is that you are unlikely, because he will immigrate soon. Unless you study abroad in the future, go to that place! Also, I feel that your personality is quite cheerful and you will meet nice people in the future. Don't push too hard. In fact, you are showing that you like him by letting him emigrate, because that will be better for his future development.