Rina Masako, who is completely subdued by her arrogant and disliked niece, in MASM-030.

I was entrusted to my niece's care for a week. I finally managed to cook her a meal, but she said, "I don't want to eat! I want to order takeout, lend me your credit card first!" She's such a hateful, bad girl. I thought that giving her oral sex would let her experience the adult world, but instead, she pinned me down, rode on top of me, and made me ejaculate inside her! She even said, "If Dad finds out, he'll kill me!" I couldn't resist her anymore... From then on, I was drained of my semen by her every day, trapped in a hellish existence.