Help!!! My Host Is Sexing A Minor... What Should I Do????

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Hello House,
I'm going to make this brief and explainable.

I have a program to run at a location and its supposed to last for six months. I wasn't having enough money to rent and furnish a place for a year since that's the minimum one can pay in that area.


Luckily for me I have a friend (Whom I'll refer to as "Mr A" who has a room to himself in that town allocated to him.

I spoke to him and he willingly and happily agreed for me to stay with him.

Now Mr A has a friend (whom I'll call "Mr B" who later became my friend too.
Mr A who is my mate is far older than Mr B.

Mr B stays with his parents and they have an only daughter who is almost 16 years old (Let's call her "Miss J". Mr B loves his only sister to the core.

Mr A started a kind of training that would lead to work and he invited Mr B to join instead of constituting nuisance at home. Mr A & B related well and did everything together.

After some time things became "rough" for us as our money got finished. My host Mr A told me not to bother organising what to eat for both of us as he will be taking care of himself. (I later got to find out Mr B's parents were constantly feeding Mr A cos they were happy he meant well for their son and also took him as their soon too)

Mr A told me how he badly wanted to "have" Miss J and I discouraged it and let him see reasons that she is still 15+, the only daughter, "our friend" Mr B's sister and her parents trust him and feed him.. I continued to kick against it until I travelled in the month of Miss J's birthday.

Sadly, I returned and told me he "deflowered" her in the week of her birthday while I was away. And since then he has been a regular visitor in between her laps.

I felt bad and still feel hurt cos its not good and I see her like my younger sister. I told him to stop or I'll expose him. We had exchange of words and I finally held my peace.

But now I'm confused.

Should I tell Mr B (our friend) and his parents?

If I tell them there will be serious "war" (if you know what I mean) and Mr A, my host will be ejected from the house meaning I'll have no where to stay too. There's no space in Mr B's house cos they are already chocked up in their house.

If I keep quiet and people find out it'll look like I've been in support of this wicked act and we might receive same punishment. (police fit dey involved)

If I talk it'll be like someone willingly offered to help and accommodate me and I paid him back by back stabbing him.

Pls what do I do?

Mature response please cos I really need it.