Season 1 of Mr. Lighter premiered on August 1, 2023.

Two girls who grew up in different single-parent families, went to the same school since they were young, and entered the same workplace as colleagues when they grew up. The two have very different appearances and personalities, and they have been fighting for more than ten years without getting tired. One day, a mafia boss suddenly appeared in their lives, claiming to be their father, but the two turned out to be half-sisters...