The boy I like sent a confession message, how should I reply? Yes or no?

You should see what kind of person he is first. Tenderness and introversion are only superficial. Do you really know him? Is he filial to his parents and teachers? What does he think of his feelings for you? Is he capable of being responsible for your feelings? Is he capable of taking care of you or raising you? These are all questions that you should consider. If you think about it, he can bring you happiness, then you can consider whether to agree or not.

If you observe that he is not very good and can't bring you happiness, then you should refuse, even if you like him very much.