This is the song "Last Regrets - X'mas Floor Style," originally sung by Eiko Shimamiya and performed by Tohru Izumi with Mai Shizuoka for this video.This is the first track of Tohru Izumi on her fictitious album "Two Shadows", besides being an adaptation remix of "Last Regrets" Original (Original Ayana and performed in a Koenma's videoclip of Mai-chan)