TOKYO — Last month, as Americans tuned in to the final episode of “Game of Thrones,” Japan was indulging in its own television fantasy world.

In this one, a woman dares to leave work at 6 p.m. sharp.

The determination of Yui Higashiyama, a 30-something project manager who wants nothing more than to get out of the office and into her favorite bar for happy hour, rocks the fictional web design firm where she works.

A conniving supervisor and overachieving co-workers try to foil her plans. When her team faces a seemingly impossible deadline in Episode 9, she puts aside her steely commitment to work-life balance, dramatically declaring, “I will work overtime!”

Ms. Higashiyama is the protagonist of “I Will Not Work Overtime, Period!” — a modest television hit in Japan that has struck a chord in a country with a dangerously intense, at times deadly, national work ethic.