Kazuhiko Nukumizu is a self-proclaimed background character, a first-year high school student who is content to observe the dramas of adolescence from a safe distance, convinced that the fleeting romances he reads about in light novels have nothing to do with him. This belief shatters one afternoon when he accidentally witnesses Anna Yanami, a popular and vivacious classmate, being gently rejected by her childhood friend. Before he can slip away, the heartbroken Anna commandeers his table, stress-eats an enormous quantity of food, and unloads her feelings onto him, leaving him to pay the bill.

As the financially indebted Anna begins sharing lunches with Nukumizu on the school’s fire escape, he finds himself increasingly entangled in the messy aftermath of romantic failure. He soon encounters two other girls in similar situations: Lemon Yakishio, the energetic ace of the track and field club, and Chika Komari, a painfully shy member of the literature club. Both are reeling from their own romantic disappointments. Lemon is heartbroken after learning that her childhood friend has started dating someone else, while Chika quietly nurses an unrequited love for the literature club’s president. Nukumizu, who initially wants nothing to do with their problems, dubs them losing heroines.

The story unfolds at Tsuwabuki High School, with much of the action revolving around the literature club, a sleepy organization that Nukumizu reluctantly joins. Through his interactions with the three girls, he is thrust from the role of passive observer into an active, if unwilling, pillar of emotional support. Rather than forming a typical romantic comedy harem, the group settles into an awkward but genuine friendship. The narrative is structured around multi-episode arcs that explore each heroine's past, the nature of her loss, and her painful journey toward acceptance, with Nukumizu acting as a confidant who helps them process their grief and find a way to move forward.

Notable arcs include Anna’s struggle to remain friends with the happy new couple, Lemon’s confrontation with her past feelings during a sports festival, and Chika’s battle to preserve the literature club and her own sense of belonging after its president graduates. While the series is a romantic comedy, it focuses less on Nukumizu finding love and more on the unconventional friendships formed in the wake of heartbreak. The season concludes with an anime-original finale that brings the group closer together, finding a sense of closure and camaraderie in their shared status as those who lost at love.