Rei: Daybreak Chapter - S0.E6

During a picnic with Keiichi, Rena accidentally swallows one of the mysterious "Fuwazaru Magatama" which falls from the sky, and begins acting lovesick. Rika explains that the seal on the magatama has been broken, and that whoever possesses the red magatama will fall blindly in love with anyone holding its white counterpart.