The lyrics speaks for itself.
Everyone was at a lost with this song.
Everyone, but Eren and Krista.
Eren just bops his head to the beat and tries to hear the lyrics and sings along with them, while Krista looks down at her hands and thinks back to her childhood.
Eren "Without love."
Pain
Krista "Can't get enough."
Pain
Eren "I like it rough."
Krista "Cause I rather feel pain..."
Eren "Than nothing at all."
Erwin "It would seem those two know that the song is talking about."
And yet they still don't know or see.