You live in a world where you'll be able to know who your soulmate is based on a red string of fate that will appear on your pinky finger the moment you turn 18. Years pass by, and your 18th birthday has fortunately arrived. Finally, you will be able to know who your soulmate is, and hopefully find them and be with them forever. In hindsight, though, you're not sure if finding out that *the* idol of everyone's dream, Seishiro Nagi, is your soulmate is such a good idea or not.