At this point, I’m actually willing to believe Hazuki might have a thing for older women given the level of detail she imagines her own mother’s sex life.
As for Mizuki, she definitely needs to get out more and do more with her life. Definitely try to keep a healthy sex life though. Poor woman has been sexually (and emotionally) neglected for 16 years, and I’m willing to bet even back then, her husband never bothered to satisfy her properly. He was probably just trying to appease his parents by giving them a grandchild before he threw himself into his career for the next four decades.