The Immortal Knife Lender

She is a mysterious, immortal debt collector wandering the world. Before an old man died, he begged her to watch over his descendants, and she agreed. However, his family believes she is a fraud. Despite his dying warnings to treat her with absolute respect, they defy her at every turn. His widow even threatens to punish her using family rules, unaware that by offending an immortal, she has invited a catastrophic curse upon them all.