Ms. Aoshika is not only divorced, but an underappreciated teacher at her job. But one drunken mishap leads her to witness firsthand the brutal assault and murder of a young man. However, after fainting, she awakens to discover that all of the assailants have been seriously wounded.
And to her further surprise, the next day she discovers that not only is the young man Akira she met the night before alive, but he is now her new transfer student.
Just read it awhile ago, pretty good.