The main problem with him is that he knew from the beginning that :1. The FL liked him A LOT2. His neighbor was…
Actually there’s clear signs that he and Rong used to like each other but they never confirmed. Both seemed to be holding out for the other to confess or for someone better. He’s the one who had a change of heart after he met FL. Such a hypocrite accusing FL of being unfaithful when he’s the one who changed first.