Lang Lang has to bear the weight of his father's death since he died when he stopped Lu Lang from committing suicide and drowning. Chaoyi is considered a coward since he "ran away" (was shipped off abroad) and didn't help Lang Lang when he needed support the most, hence why Lang Lang said although he knows Chaoyi isn't at fault, he can't bring himself to forgive him [Chaoyi] since it was really all his [Lang's] fault but that's a responsibility that's too hard for him to carry

Ok I'm lost... What did ChaoYi do that made him a coward?? And what kind of responsibility did Lang Lang have to bear?? Can anyone please help me out?