In the upper right corner, I have obviously seen that scene in the original game, but it has not been unlocked.
KulPlant's adult fan creation of Dragon Island · By
If some scenes aren't unlocked for you while you had already seen it in the original game, try go into the original game, load a save that have that scene unlocked and skip to any ending. If none of that works, quickly go through the game or load old saves to see those scenes again will always unlock it here.