As of my last update in October 2023, Midnight, also known as Nemuri Kayama, is ranked as a Pro Hero in the "My Hero Academia" series. Specifically, her hero rank is typically noted to be in the top tier, though the exact numerical rank can vary in different parts of the story. She has been shown to be a competent and skilled hero, known for her quirk, "Somnambulist," which allows her to put others to sleep.
For the most accurate and up-to-date information on her hero ranking, it's advisable to refer to the latest chapters or episodes of "My Hero Academia," as rankings can change based on the narrative developments in the series.