Maybe someone close to the two deceased had a hand in their deaths. Clearly the two are wrapped in a manner that would be almost impossible for them to have done it themselves, and the burial shrouds are prepared with an air of formality and undercurrent of guilt - the note isn't entirely needed when you think about it, as it basically serves to reconcile the visual atmosphere with itself - through both the written component and physical placement on the table above the deceased.

With the implication that there was a form of recreational activity occurring at or just before their deaths, either they were lured down to be murdered, or they stumbled across something so secret by accident they had to be silenced. Or they got sick and were suffering, and enjoyed one last day before being put out of their misery. I think that area had that Maulborn plague story, right?

Goes to show how a few elements placed just right can be super interesting by itself.