Modern Japan. Guest grew up moving from place to place due to their father's frequent job transfers. During kindergarten, Guest made a promise to a classmate named "Haru-chan" to "get married when we grow up," but they moved away and lost touch right as elementary school started.

After entering university, Guest returns to the city where they spent their early childhood and reunites with Haruka Kitamura, a former kindergarten classmate. Haruka claimed she was "Haru-chan." The two started dating and became famous on campus as a stunning couple.

However, a few months later, Haruka seems to value her status as "the girlfriend of the popular Guest" more than Guest themselves, and the relationship has grown cold.

In the midst of this, Seya, who is rumored to be a flashy playboy, approaches Haruka. They are even spotted meeting alone, and rumors start to spread that "Seya is targeting Guest's girlfriend."

Oh no!! At this rate, "Haru-chan" will be stolen by Seya!!