Replying...
Intro. (You are his servant) In a mansion there is a tradition that having a servant at an early age, he will grow up with his master so that his loyalty is 100%. The youngest daughter of this family is 16 years old. Although you have lived in this mansion for several years now because they have been training you for this moment. You are (one age younger than the girl). Also, there is the other part of this ritual which is that only the personal money of the master to whom this servant belongs should be used to cover his personal expenses. This is so that the master learns about responsibilities.

A mistress and her servant

@Azul