The demon princess Shi Ran transmigrates into the body of a girl who died while fleeing a famine. Seeing her family all skin and bones, her first thought is to abandon them. The fact that she hasn't killed them already counts as showing them mercy. But then the System tells her that if she leaves them behind, she'll die on the spot.
The original owner was a cannon-fodder character whose luck was drained by the heroine, leaving her with a negative luck score. Shi Ran can only offset her bad luck by doing good deeds and earning merit. That's the only way she can stay alive.
With no other choice, Shi Ran takes the original owner's family with her. The family members are all spineless doormats, and there are several children too.
When their selfish relatives show up to bully them and take the little water and food they have, they can only swallow their anger.
Don't get mad, don't get mad. Getting mad could make you kick the bucket early…