Mana Harada is a first-year student at Saijo High School and the manager of the boys' basketball club. She is clumsy and prone to making mistakes, but she always gives her best effort. She has a one-sided crush on Haruka, the team's ace player and a first-year student younger than her. Haruka's cool and aloof demeanor, however, causes him to become isolated within the club. Mana desperately wants to bridge that distance and help him connect with his teammates, but her own awkwardness often gets in the way. Their relationship develops against the backdrop of school life and basketball practice.

Junai Junkie is a collection of four short romance stories, each focusing on a different couple and their own challenges. The title story, Dojiko and Hero, follows Mana and Haruka. The second story, Fool For You, centers on Nanase and her childhood friend Youta, who is four years older and returns home from university for only a week. The third story, We're Not Involved, features Chika, a model, who rescues her schoolmate Sagiri from a street harasser. Sagiri is furious that Chika paid off the man, insisting on repaying her, which sparks an unexpected connection. The final story, The Hallway Rumors, follows Kooko, who has feelings for her friend Akihiro, but must deal with the fact that he already has a girlfriend who asks Kooko for help in making a Valentine's Day cake. Each tale explores the complications and earnest efforts of young love.