Serving the family of someone you caused the death of.
"It came to pass that her carelessness cost her sister her life. From that point, that once free-spirited woman realized she had created a debt to her sister's new family that could ... never be repaid."What is a person to do when they cause (directly or indirectly) the death of someone who has a family? Why become their family's servant of course! Whether or not the family is aware of the reasoning is irrelevant. A Sub-Trope of The Atoner. Compare and contrast I Owe You My Life for when they become the servant of someone who saved their life.
-- Shinobu, Kyon: Big Damn Hero
Examples of this Trope include:Anime and Manga