Hirukowashi-hen is based on Higurashi Daybreak. The main characters are Keiichi Maebara and Rika Furude, and this story is set in a parallel world. One day, Rena accidentally swallows something in her mouth during her usual treasure hunting. According to Rika, the seal of the sacred "Fuwarazu Magatama" pairs were broken and Rena must have accidentally swallowed one of them. The magatama holds mysterious magical powers in which a person that has the red magatama will blindly fall in love with anyone with the white magatama.

(Source: Wikipedia)