Does the good ending have anything to do with inputing Haruka's real name in the beginning? That was my thought, but I can't get any dialogue that mentions her real name.
Ok, so it was where I thought of to find it at first, but here's something to note: you can only find it if you download the PC zip file. Mac users don't have the necessary information.
technically there's 3 endings-ish (i guess more like 2.5) because if you enter the correct name at the beginning of the game, or at the ending of the game, the dialogue is slightly differed