Somethings Wrong With Us Graphic Novel Volume 18

Nao and Tsubaki are expecting a child and the couple is overjoyed. Unfortunately, their happiness is cut short by an invitation to meet with the Proprietress's family, whose members are less than happy to learn about the couple. Amidst this trouble, the Proprietress herself reappears after a long absence. What could she be plotting, and how is it connected to the mysterious girl Nao met recently?