The following is a list of characters that have names, but little to no significance in any major route.
???/Disembodied Voice
??? is a disembodied voice and the first "character" to appear upon starting a new game. They allow the player to choose their gender and which graphics they prefer, they explain how to save, and they provide narration for a couple of scenes, albeit in an adversarial way akin to The Stanley Parable. Because of this, only the protagonist is aware of ???. Some unnamed characters are also referred to as ???. This section does not refer to those students.
Hilent
Hilent is a student who wants bigger breasts so she can be more like Dr. Tiff. She appears twice. The first time is during the Bimbo Teacher route, where Ms. Rack teaches her a breast enlargement spell. The second time is during the Hospital Harem route where she visits Dr. Tiff because her breasts won't stop expanding. She is named after one of the artists for the game.
Jasmine and Talie
Spoilers for the Berserker and Intelligent Monster routes.
Jasmine and Talie were Ashley's friends and party members until they all went missing in the dungeon roughly a year prior to the events of the game. They were turned into breeding slaves by the Frost Queen.
Sarah's Mom
When Sarah was little, her mother died when a monster attacked their home. If the protagonist accompanies Sarah to her home, that same monster will return, and nearly kill both of them. At the last minute, Sarah will be possessed by her mother's ghost, who saves them using a bubble spell. The protagonist can then enslave her, unlocking the possess spell.
Sarah's Dad
Sarah's dad was presumed dead in the same attack that killed her mother. He isn't. If the protagonist refuses to accompany Sarah to her home, he will be the one to rescue her from Bear Claw.