The heroine has always felt excited seeing girls in horrible situations.
However she has never been able to voice her desire to be treated the same way, so she would read hardcore R18 manga to satisfy her unsavory urges.

One day she bumped into her neighbor who always gives her a cheery hello at her apartment complex’s elevator.
He picked up her phone when she dropped it and proceeded to see the hardcore R18 manga page she was reading the day before.

“My life is over…”
Trying to deal with the stress of her masochism being discovered and her unforgiving workplace, she went to an Izakaya to get a drink where she happened to bump into her neighbor.
As they drank together, she felt very awkward. However, his Golden Retriever-like personality allowed her to eventually open up about things she’d never told anyone to him.

“I'm doing as you said.”
“When I asked if you wanted me to try stuff out with you, you said gladly.”

She woke up in a hotel bed to the feeling of pleasure as he stood over her making her violently cum with his hands.

“Wow… You really do love being treated roughly.”
“Please teach me more about your perverted fetishes.”

While unsure why, she was unable to resist the temptation to continue with this relationship with him, and thus they continued to do it again and again.

Though as time went on, every time they met up, the things he wanted to do got more extreme. As did the things he’d say and do.

The mixture of fear and pleasure she felt as he remodeled her body led her to decide this relationship wasn’t good for either of them and put a stop to it.

“Let's go back to a normal relationship.”

His eyes darkened as she said that.
He dragged her into a hotel and put her through cumming hell. It was then she came to learn about why he was so obsessed with her.

“You've given me some wild fetishes, and now you're the normal one. I can't tolerate that.”

Her masochism drove him insane, and his obsessive love made her learn who she truly is.