A Good Day to Be a Dog centers on Han Hae Na, a single high school teacher carrying an unusual family secret. Due to an ancient curse, any member of her family who kisses someone will transform into a dog at midnight for six hours. This magical transformation repeats every night until the cursed individual, in their dog form, manages to kiss the very same person again. This bizarre condition has sabotaged Han Hae Na's romantic life, as her plea to potential partners to avoid kissing always leads to their departure.
One fateful, drunken night, Han Hae Na accidentally kisses Jin Seo Won, a fellow teacher at her high school whom she isn't even close with. Panic sets in as she faces the nightly transformation. Desperate to break the curse, she persistently approaches Seo Won, hoping for another kiss. However, her quest is complicated by a significant hurdle: Jin Seo Won harbors a deep-seated fear of dogs, making her mission to end the curse much more challenging.