Diary Of A Void by Emi Yagi

A woman in Tokyo avoids harassment at work by perpetuating, for nine months and beyond, the lie that she’s pregnant in this prizewinning, thrillingly subversive debut novel about the mother of all deceptions, for fans of Convenience Store Woman and Breasts and Eggs
When thirty-four-year-old Ms. Shibata gets a new job to escape sexual harassment at her old one, she finds that as the only woman at her new workplace—a manufacturer of cardboard tubes—she is expected to do all the menial tasks. One day she announces that she can’t clear away her coworkers’ dirty cups—because she’s pregnant and the smell nauseates her. The only thing is . . . Ms. Shibata is not pregnant.
Pregnant Ms. Shibata doesn’t have to serve coffee to anyone. Pregnant Ms. Shibata isn’t forced to work overtime. Pregnant Ms. Shibata watches TV, takes long baths, and even joins an aerobics class for expectant mothers. She’s living a year of rest and relaxation, and is finally being treated by her colleagues as more than a hollow core. But she has a ruse to keep up. Before long, it becomes all-absorbing, and with the help of towel-stuffed shirts and a diary app that tracks every stage of her “pregnancy,” the boundary between her lie and her life begins to dissolve.