Otome-san vs. Kowai! Otome-san is a term for mother-in-law, while Kowai, which means scary in Japanese, stands for the daughter-in-law. Mizusawa Asako has been living under the constant nagging and criticism from her mother-in-law, up till the old woman's death two years ago. Just when she can start to relax and enjoy being the mistress of the house, her only son informs her that he is marrying a girl named Ririka. Both Asako and her husband, Hiroyuki, are against the marriage, but to no avail. Thinking of scaring Ririka, Asako tells her that they will accept her as their daughter-in-law, on the condition that the newlyweds move in with them. Ririka smilingly agrees to it, and thus they are married. Asako is determined to be a good mother-in-law, but feels apprehensive about it all.
On the first night the newlyweds return from their honeymoon, Asako finds herself alone with Ririka, with both her son and husband staying out late. They started drinking together, and soon Asako and Ririka are hitting it off! The next day, waking up with a hangover, Asako finds that the breakfast has been made, and the cleaning all done. Ririka seems like the perfect daughter-in-law. Or is she? Strange disappearances start happening in their neighborhood, and Asako starts to distrust Ririka more and more...