Hey Apis4!
Outside of a few scenes: Rae has one or two when its just the both of you in the house at the start of the game that can be missed). Lyriel has a dream scene where you can miss a scene depending on whatever route you take in that dream. The trio of gals at the start in the park, and the poolside dream with Jenny & Vivian (depending on who you pick of course).
Everything else should be unlockable!