In-depth information for what happens if you enslave Cassandra and make her into a willing slave.
For a rough outline, refer to the general willing slaves page.
Note that this is just a general outline for what happens during the route. It is not a walkthrough.
Meeting Cassandra
The Protagonist can meet with Cassandra in two possible ways.
The first is by being friends with Sarah and watching her scenes until Cassandra bullies her in Drape's classroom. The Protagonist chooses to break up the argument, causing Sarah to get somewhat disappointed as she was planning on hitting Cassandra with a spell.
Otherwise, the Protagonist needs to have enslaved Julia and changed her into her Fanatic form and spoken with her in the hallway, telling [Julia] that [the Protagonist] would take Cassandra on easy.
Target for bullying: Cassandra
After refusing to revert her back to normal, Cassandra begins walking around school in her new form, being mocked by her former friends and her classmates. The Protagonist can either comfort her (+affection) or mock her (-affection) but either way, the Protagonist leaves.
Cassandra's Plea
Cassandra confronts the Protagonist, asking if she hasn't been bullied enough. The Protagonist disagrees with this and says that she can simply visit Dr. Tiff, but Cassandra explains she's too terrified of visiting Dr. Tiff to even consider going there. The Protagonist explains it's her problem and leaves.
Continued Bullying
The Protagonist soon overhears some students talking, Cassandra seemingly kneeling on the floor, still being bullied by the others. She asks the Protagonist if this is what the Protagonist wanted to begin with, but the Protagonist calmly corrects her, saying that s/he never had anything specific in mind for Cassandra to begin with. Cassandra, desperate to turn back to her normal form, asks for the Protagonist to revert her back to normal. The Protagonist tells her to meet him/her at the Protagonist's house.
Willing Slave Cowsandra
Back home, Cassandra asks the Protagonist once more to revert her back. The Protagonist can choose to do so, saying she has suffered enough, enslave Cassandra or tell her to become his/her servant.
Choosing the third option causes Cassandra to panic but then asks for how long. The Protagonist says it'll last until the end of the school year. Cassandra, very reluctantly, agrees to becoming the Protagonist's slave.
Obtaining the Milk Pumps
With Cassandra in the party, the Protagonist heads to the thirteenth floor of the dungeon and finds a treasure chest. They realize it's milk pumps and the Protagonist teasingly presses it against Cassandra's boob, which causes her to moo. They head back and the Protagonist decides to use them on Cassandra, after cleaning them. However, using them too much will cause damage that won't be possible to revert.