It's a comedy about a 28-year-old called Tsubame Kamoi, who's deeply attracted to very, very young girls. Might say the following to them (and these are quotes):
"Don't tell me you don't like girls who've started menstruating either?"
"I promise to love you, even after you start having periods!"
"Here's a balloon, along with my LIME messenger info and phone number."
Questionable taste? Yeah. Funny? Definitely. The show would have been terrifying and unwatchable had Kamoi been male, but she's not. She's a maid. She's still appalling and sometimes creepy, yes, but it's obvious that Misha's in no danger from her. On the contrary, you couldn't find a more vigilant guardian. Kamoi's an ex-soldier with muscles on her muscles, so you'd probably be safe with her even if you'd got lost in the mountains and were facing a mother bear. (This happens.) Kamoi is also super-competent, a fantastic cook and the kind of person who'll make all your friends think she's wonderful. She genuinely is devoted to Misha and will help the girl get over some of her issues, face up to grief and become a better person.
That said, though, she's also got the common sense of a toenail. She never realises that her antics are deeply unacceptable, while Misha's extreme bluntness to her is only partly an expression of a troubled personality. It's also because you'd need a ground-level nuclear strike to get any reality into Kamoi's skull.
As for Misha, she has two personalities. When her mother was alive, she was warm and happy. That Misha no longer exists. (We've no idea what happened to her biological father, by the way, and the only family she now has is her stepfather.) The Misha we meet in ep.1, on the other hand, is a brutal little monster who takes pride in having driven off all other maids until now. She doesn't go to school and instead just slouches around the house all day, playing computer games. It's been so long since she had any friends that she talks to animals instead. She hates Kamoi on sight, obviously. She hates everyone.
Kamoi helps fix a lot of those flaws. It doesn't take long for Misha to go back to school, for instance. (If you had Kamoi waiting for you at home with marriage papers, you'd go to school too.)
This is funny. It probably shouldn't be, but it is. Misha finds Kamoi annoying and regularly orders her to drop dead, go to prison, etc. Kamoi though is enchanted by all this and repays Misha with: (a) intelligence, consideration and back-breakingly hard work in all her duties and (b) mental stalker behaviour. (Her military training makes her a modern ninja who can appear anywhere without warning, for instance.) Neither person has any filters at all, Misha because she's rude and Kamoi because she's deranged. You could carry a full comedy season just on these two, which is more or less what happens... but there's a fun supporting cast too. Ukai Midori is another ex-soldier who's in love with Kamoi and won't take "no" for an answer. (In fact, Midori's a masochist who gets turned on by being insulted, shot down and treated as a pervert. Kamoi never sees the irony.) Then we have Misha's classmates, once she's gone back to school. Washizaki is a nice girl who lacks confidence, whereas Morikawa has a Godzilla-sized ego and sees Misha as a rival. (To her frustration, Misha doesn't get it and couldn't care less about Morikawa's challenges.)
Is any of this realistic? Not really. If it were, the show would shatter into tiny, terrifying pieces and be radioactive. Misha has Dr Dolittle powers, for instance, which might be why her pet ferret never eats her pet hamsters.
Counter-intuitively, it's a heartwarming show. Misha isn't nasty underneath, really, and her character growth will lead her into, say, being supportive of the insecure Washizaki and even guilty about mistreating Kamoi. (At one point. Briefly.) There's character depth here, as well as low gags. Misha's likeable enough for you to be happy for her growth, but also brutal and rude enough to be a great comic foil. The inappropriate comedy isn't as extreme as it could have been, really, and this is a very funny and bizarrely likeable show.