
Cain approach Jooin because in the I think it was the dynasty era they use to be owner and dog. Dog (cain) loved his owner to death, saw him di3 and his owner said to him that he wanted Cain to live a joyful life before dying and leaving him alone. In this lifetime, Cain doesn't want to tell Jooin because he fears he will react like his family. (Accuse him of being delulu).

What I means is how Cain and Yahwi reacted to Jooin not remembering the past. Jooin doesn't remember having a past life with Cain who was his pet dog nor remember meeting Yahwi when they were 4-5 years old. The difference in reaction is Yahwi told Jooin about it and used it as sympathy, he treated Jooin badly simply because he didn't remember (he now regrets it). With Cain, Cain refused to tell him because it will lose meaning, he rather Jooin remember own his own and even if Jooin doesn't remember Cain was respectful and is ready to leave for Jooin sake.
As someone who read the next chapter, I'm curious what yall would think about Cains thoughts, to me it shows a parallel to yahwi on how both react to Jooin not remembering the past