During the 3rd phase of the final boss, after using Annihilation, two characters will talk, and the first character that talks will be the character that you will get an ending with. You can only get 1 ending every time you beat the final boss, bar Relia's ending, and it's all dependent on the affection that character has with you. It is important to note that the game prioritizes the characters in the following order, should more than one of the characters have the same number of affection points: Miki > Fiore > Anne > Victor > Emmerson.

In order to raise affection, you must do the many Private Actions with the characters throughout the game, and on occasion, answer a question. Answering with a favorable answer will raise affection, and answering with an unfavorable answer will lower it. You can also use the Love Potion No. 256 to raise affection and Emotional Destabilizer to lower it in order to manipulate what ending you get.