Do M Imouto no Roshutsu Yuugi ~Dare ni mo Ienai Himitsu no Asobi~

My little sister, Miku, is friendly, flawlessly beautiful, and has excellent grades.
There's no end to her good points; she's truly beautiful and intelligent.
But one day, I discovered a shocking secret.
(You've got to be kidding me... that Miku...!)
Miku had uploaded a video of herself masturbating in my room to a video sharing website.
Why was Miku filming herself masturbating?
Why was it filmed in my room?
All sorts of thoughts flooded my mind, making it a mess.
I considered calling Miku and asking her directly.
But asking her, "Were you masturbating in my room?" would undoubtedly create an awkward atmosphere.
"In that case, there's really only one way to find out the truth.
That's right... I just need to capture the moment Miku enters my room.