A "knocker-upper" is someone who has awakened to the ability to destroy the weirds that appear from nightmares. When Reina is discovered by Tris to have this ability, Ryuhei asks Reina to help him solve the mystery of her brother's death, as he thinks that the rumoured Somnium Drop candy in town and the sign of a mysterious incident have something to do with it. At the same time, Reina, who is popular on social media, gets into unexpected trouble.