Chiho is a young woman who loves her job, and Natsu is her devoted boyfriend who loves her. They are both 156 cm tall and have always been close friends, but recently Chiho has begun to feel cramped and uneasy when she is with Natsu, as if their relationship is becoming constricting. Just as she worries that she might not be able to stay with Natsu, an extraordinary event solves all her problems: Natsu suddenly shrinks from 156 cm to a mere 13.5 centimeters, becoming a tiny, miniature version of himself. Now Chiho must navigate her feelings for her shrunken boyfriend while dealing with the arrival of a handsome new coworker, Negishi, at her workplace. The story follows the unusual romantic comedy and daily life of a super herbivore (passive) boy and a career-driven girl as they search for eternal love in a world where physical size no longer matches the size of their feelings.