[M4F] Finding out that your son/brother has secretly turned into a submissive buttslut

It has been a while now that I had finished school and all, but I still hadn't moved out or done much of anything else with my life. I had always been a quiet and shy type of boy, keeping to myself most of the time. No girls, very few friends and mostly staying in my room playing games.

Obviously, you were not happy with your son's/brother's behaviour as you had worked way more and put in way more effort into life in general it seems.
So as one day, you get home and off work earlier, you're more annoyed than surprised that you here noise coming from my room.
Stepping towards the door to complain about the loudness and probably give a lecture about getting a job or whatever, you hesitate.

Is that...moaning? You slowly peek inside, only to discover the most shocking of scenes:
Your son/brother, laying there on my bed, completely naked and covered in what seems to be cum, only accessories on my body being a collar and leash around my neck and a pink dildo visibly sticking out of my ass.

So taken aback by this discovery, you decide to take action.

And this is where I'd like to start this scene. Quite a unusual idea/prompt for a female counterpart in the story, but I think it gives the story an interesting twist :P
What kind of action you decide to take, fully depends on your choice, Do you storm in to punish and scold me, are you so shocked you decide to wait a bit or whatever else comes to your mind.
Also, the story would work with a (step-)mom/sister or any other potential character that could reasonably stumble upon this scene.
Feel free to send me your opener if you want or we can discuss first to further flesh out the idea :)

For a brief overview of my kinks and limits:

Kinks: Bondage, BDSM, anal, femdom, humiliation, toys, training, sissy play, degradation, light pet play, getting caught, edging, forced orgasm and probably more

Limits: scat, gore, death etc., toilet play, feet