@Blue_desire It’s just he is still innocent and a child infront of Tia. But after graduation he would have to work so much that he might not smile that brightly again and he would officially be an adult. And no, nothing negative happens to him in future, so don't worry.
I like to post spoilers for the stories I find interesting because I don't have much time to read novel due to busy schedule you will find me in most romantic historical manhwa comment sections