This DLC is Chapter 5, "The Chaotic Choir Concert," of The Grade 5B Case Files. With the New Year approaching, Baker Elementary's annual New Year's Choir Competition is about to begin, and every participating grade has already started rehearsing their songs.

Before the competition, however, the Choir Costume Design Contest is also held. Students from every grade are invited to submit their own costume designs. After the voting concludes, the winning design will be brought to life, and the choir performers will wear the selected costumes on stage.

Watsonia also submits a costume design of her own, hoping her irresistibly "cute" creation will win the vote. Yet amid the lively excitement surrounding the event, Holmlyn once again catches that faint trace of noise within the school—as if, hidden among the beautiful harmony of the choir, someone is quietly singing a discordant note.

Holmlyn: Watsonia, you should head home first. There's something I still need to take care of.