Slave Rain

The author's character book description of Slave Rain for Part 2:

"The drops of corruption that serve the lord!!"

"It was too difficult to defeat the strongest magical girl, Arti Rain, by brute force, even when she got attacked by Cherry's particularly vicious tactics.

But Rain falls into a trap that takes advantage of a slight emotional opening in her heart, and she is gradually transformed into a suitable female slave both in mind and body by hypnotic conditioning without even realizing it.

Her breasts, in particular, evolved into a ridiculously huge size beyond what she could have ever imagined, in order to satisfy her new master's desires. The pleasure brought by her lewd magic milk lactation melted away even the protection of the spirit that her late father, who she respected, had left in her gear.

Finally, she was completely corrupted into an obedient and loyal female slave named Slave Rain. Fallen Rain was freed from her previous heavy responsibilities and finds unparalleled joy in living solely for her new master's sake.

Not only her once-renowned abilities as the First and Strongest Magical Girl but also the enormous power she once hesitated to wield out of fear are now eagerly used by her to please her master and punish anyone who defies him."