Seong Je was the better friend for Baekjin than Baku.
I understand Baekjin and Baku were childhood bffs and they were one another very first bestfriends but eventually Baku stopped knowing Baekjin.
Baku wanted a friendship with Baekjin who was the boy who used to admire him and someone who he had saved from bullies and his loneliness of no friends. Basically Baku as the Hero in Baekjin life.
However Seong je knew the TODAY Baekjin, and he accepted him for his good and bad. Seong Je even knew Baekjin had this weird obsession (ex lover bond) as he would joke about as well with Baku x he never judge him or made it weird for him.
Even when Baekjin hurt his feelings, Seong Je was a bit spiteful but in the end he didn’t gave the evidence over and he did went looking for Baekjin himself and when the boss ask him “are you Baekjin friend?” He said “yeah” and even ask him out of real concern for Baekjin whereabouts.
I truly feel Baekjin was chasing a ghost of Baku and he should have gave a real chance to Seong Je as a friend. Especially considering Baku has no problem giving friends chances, especially siuen lol.