Yui Saikawa, a middle school idol, suddenly appears in front of Kimizuka and Natsunagi. Saikawa receives a letter that said, "I will receive a sapphire with a market value of 3 billion yen on the day of the concert at the dome." Kimizuka and Natsunagi accept Saikawa's request to inherit Siesta's wish. However, during rehearsal the day before the concert, a mysterious man approaches Saikawa on stage.