Jaheon was the one responsible for taking care of the pot mugo was trapped in. During those times, they formed a sort of friendship shared between two people in misery (parallel to the current one). The "sin" that the main branch talks about, and why jaheon's branch family was treated cruelly and sacrificed, is instigating mugo to take revenge (ch. 9). But the other mugos don't remember this, only the 4th one.
Jaheon was the one responsible for taking care of the pot mugo was trapped in. During those times, they formed a sort of friendship shared between two people in misery (parallel to the current one). The "sin" that the main branch talks about, and why jaheon's branch family was treated cruelly and sacrificed, is instigating mugo to take revenge (ch. 9). But the other mugos don't remember this, only the 4th one.