My Love Mix-Up! follows Atom, a shy high schooler with a big crush on his classmate, Mudmee. One day, he accidentally discovers that Mudmee has written the name of Kongthap, the super cool basketball player, on her eraser. In a moment of clumsiness, Atom drops the eraser, and Kongthap sees his name on it, misunderstanding the situation and thinking Atom is crushing on him.