You are Ms. Servant Kimi wa Meido-sama.

This is the story of a maid who is all alone in the world, but who finally finds a family.

Told from young that her only worth is as a killer, Yuki had known nothing else except cold efficiency and following orders. Now that she has a chance to leave her past behind, she arrives at the doorstep of Hitoyoshi Yokoya, asking to be employed… as a maid?! Thus begins the journey of a former assassin learning what it means to be ‘normal’!

(Source: Shogakukan)