You are Ms. Servant

A maid suddenly appears at the house of high school student Hitoyoshi Yokoya, asking to be hired. However, her background as a former assassin makes Hitoyoshi think twice. From this fateful encounter, their lives together will forever be changed.

One day, Hitoyoshi is compelled to adopt a puppy that was left in front of his home. However, the maid has a childhood trauma involving dogs. Watching the two interact, the maid soon sees the world in a new light, even wishing to be "normal" herself.

Riko, Hitoyoshi's younger sister, pays him a visit to see the new puppy. As a lover of beautiful women, she easily gets along with Yuki despite her being a former assassin. In awe at Yuki's skills, she decides to use her for a school assignment.

To experience a "normal" school life, Yuki enrolls at the same school as Hitoyoshi. Seeing boys rush off, she finds out the school store sells a rare yakisoba bread. Yuki heads out the window, leaving Hitoyoshi to worry whether she'll fit in or not.

After the Nitta incident, Yuki decides to become Hitoyoshi's bodyguard, sticking to him 24/7. When she is distracted for a moment, a woman named Grace appears and takes Hitoyoshi hostage, seeking to kill Yuki for prestige and revealing her dark past.

Finding enjoyment in teasing the former assassin, Grace returns as a gym teacher. After much harassment, she clues in Hitoyoshi of the changes occurring to Yuki. He now wants to know more about the maid as he sees her working hard to be normal.