From MangaHelpers:
Kimihiro Sekiya is a normal salary man, living alone in his apartment, with a reasonably normal life. One night, a “stray” maid appears at his front door, telling him that she is a maid sent by his grandfather. Naming herself as Rin, she explains that in the past, she and Kimihiro played together when he was young, but he doesn't recall such memories. Even so, he accepts this maid. But what is she capable of? She is very spontaneous, ditsy, too energetic, and lacks the delicate skills of a normal maid, making her more like a burdensome maid. How will Kimihiro live his life with such troubles and will Rin be able to please her new master?