"LUCA" (Last Universal Common Ancestor) is based on Charles Darwin's proposition that all species of life have descended over time from common ancestors.

Today is righteous Chae-young's first day of her transferred school after beaten a bully to nothing. Despite the dad's warning, she saves her classmate Jong-gu from bullies again. Fascinated by her, Jong-gu asks how to be strong like her.

A vida aparentemente normal de uma adolescente com um passado misterioso se transforma quando um grupo de estranhos aparece provocando transtornos indesejáveis.