A shy, awkward boy named Ai has a crush on the most popular sweetheart, Victoria. Amae, older sister of Ai and known for her extreme delinquency, is drawn to the school's perfect prince, Logyn. By a quirk of fate, both entered a pact of "Siblings in Love" and vowed to help each other win their dream dates.

Through this youthful rite of passage, their siblingship evolves from strangers to comrades and in turn, the two learn what it means to truly love someone.