Manaka Kawashima, a high school girl, is in love with her childhood friend and classmate, Ei Eguchi. She continues to think of him with single-minded devotion… until another heroine, Ayame Takabi, suddenly transfers into their class.

Unlike Kawashima, however, Takabi is a natural-born winning heroine: on the very morning of her transfer, she bumps into Ei-kun on the way to school, gets a lucky perv moment, and basically hits every classic rom-com flag right out of the gate.

Kawashima falls into despair… but then the story’s background character MC, Kimura, decides he’s going to fight to guide her from being a losing heroine to a winning heroine…!?