OVA: A secret you can't tell anyone - S1.E1

A kind and reliable older sister, Mizushiro Ayaka. A younger childhood friend and now my girlfriend, Tsurutani Ayaka. While I'm happily getting along with the two, I wasn't satisfied. That is because I have a hobby that I must keep hidden.

I want to do S&M.

I secretly buy tools for my personal use - stare at it, touch it. And then one day as I was expelling myself of my urges, I noticed that someone had entered my room and saw the secret.

Let's try setting a trap...

I turn to see who discovered my secret. And so, our abnormal relationship began.