In a peaceful day like any other, a small box was dropped on Rika Furude's head when she was sweeping in the Furude Shrine. In it was a pair of magatama, one red and one white. The magatama is actually the sacred treasure of the Furude Shrine. With its magical powers, the holder of the red magatama would unconditionally fall in love with the holder of the white one. Upon testing its effects on the school faculty, the club members of a Hinamizawa school decided that they should duel each other to see which pair gets to keep the magatama. In the beginning it was only an afterschool club activity, but their game eventually engulfed all of Hinamizawa.