Despite not understanding much about fleeting teen romance, first-year high school student Kazuhiko Nukumizu still wonders how he would react if his life were to be turned into a love story. Regardless, as a self-proclaimed "background character," Nukumizu is satisfied continuing his life as an introvert with a negligible social life. However, he suddenly finds himself too close to the spotlight when he witnesses his popular classmate Anna Yanami be rejected by her childhood friend in the middle of a family restaurant.

While Nukumizu wishes he could just forget what he saw and move on, Anna ends up forcefully confiding herself in Nukumizu, lamenting her status as a childhood friend fated to have her beloved stolen. As he becomes dragged into Anna's situation, Nukumizu soon gets caught up in the relationship drama of two more girls: Lemon Yakishio, an outgoing member of the track and field club; and Chika Komari, a shy member of the literature club. Now thrust out of his comfort zone, Nukumizu finds himself a major character in the lives of too many losing heroines.