Why not just tell him?
i think the view might come from different experience, i met people who would be completely blind even when faced with the fact about other person, denial is strong especially if you are attached to someone but story wise, its just another BL that puts another love interest as an easy conflict so its obvious that the author does not want proper communication that definitely always annoys me about those webtoons but oh well
Jian yi is kinda sexy when he's handling Xi xi with such confidence