A high school student, Shirase Koharu, helps out at an onigiri shop that was opened by her mother, who passed away three years ago. While assisting her father in running the shop, Koharu also takes care of her two younger brothers, leading a hectic and demanding daily life. One day, Koharu receives an unexpected proposal from a regular customer of the shop, the novelist Kurosaki Ayato. Out of nowhere, he says to her, “With these one billion yen, please marry me.” Faced with this sudden and unconventional proposal from Kurosaki, who has zero experience in romance, Koharu finds herself gradually shaken by his completely unpredictable approach and her heart beginning to waver little by little.