Bloodstained Ring (血痕指輪, Kekkon Yubiwa) is a series of songs by diarays. The title of the series is a word play The word for Wedding Ring (結婚指輪) and Bloodstained Ring (血痕指輪) are pronounced the same way but written differently. It references and is possibly connected to kou's other two series, Diary of Oblivion and Despair Vaccination. The official playlist is on YouTube.