Tobira wo Akete is neither forgotten classic nor a diamond in the rough. Feel free to skip it.

Yet another story about transporting characters from mundane world to a fantastical one. I barely forced myself to pay enough attention as the plot waffles about. Plot twists and surprises feel stale and hollow.

Only watch it for the sake of nostalgia, if applicable. Otherwise try some other fantasy, for example "Lodoss tou-Senki" ("Record of Lodoss war") or "Fire and Ice 1983".