ADN-666 Despite having a fiancée, I was tied down by an unremarkable and taciturn coworker who milked me for all the semen. Story by Tsubaki Miyahara.

I jokingly invited her to a meal, and she actually said OK!? The unassuming, quiet, and intimidating atmosphere of Miyamiya-san never would have led me to believe she'd accept the invitation...
I already have a girlfriend, so I thought we'd just eat at a family restaurant and call it a night, but then she invited me back to her place for drinks...
I figured if I could get laid, that wouldn't be bad, so I accepted, and we ended up having sex at her house.
The next day, Miyamiya-san actually thought we were in a relationship...