Rhymes

Murders are happening and no one has any clue why or by whom. With every murder, they get a note with a different rhyme each time. But suddenly the notes are getting to them before the murder happens.

Is that a threat by the murderer or a clue by an anonymous helper?

And it isn't helping Taehyung at all that a teacher seems more important to him than the case, so much that he can drop the case for him.