I currently have all character's events and main events done, but I'm missing a secret event. The Fortune Teller mentions that I can still improve my relationship with Vivi if Glace is Celica, but I have done all scenes related to them, or at least I haven't found any new scene when wearing Glace or letting her control Celica. My best guess is something related Mirania, but I have defeated her and also give up to her and nothing works (awesome game btw~)