Masochistic little sister’s exhibitionist play

Description: My little sister, Miku, is friendly, has perfect beauty, and gets great grades.
There’s no end to her good points, she’s truly intelligent and beautiful.
But one day, I found out a shocking secret.
(No way… that Miku…)
Mikuru had uploaded a video of herself masturbating in my room to a video sharing site.
Why was she filming herself masturbating?
Why was the video filmed in my room?
All sorts of thoughts came flooding in, making my head a mess.
I considered calling Mikuru and asking her directly.
But if I asked her if she was masturbating in my room, it would definitely create an awkward atmosphere.
"So, that’s the only option…"
There’s only one way to find out the truth.
Yes… I just need to capture the moment Mikuru breaks into my room.