On the day of her high school entrance ceremony, ordinary high school girl Akari receives a marriage license application from the strikingly beautiful Runa Kiyozumi. Akari is bowled over in shock, and that's before Runa shows up at her house! A torrential downpour means Runa can't go home, which means one thing: time for a sleepover! Add Mochi, Akari's stuffed animal and imaginary friend who loves to ship people, into the mix, and things are sure to get even more complicated!