 

This is a very long story so I will try my best to make this as concise as possible.

1. My wife (21F), her sister (18F), and I (23M) had plans to go see a movie tonight.
2. My wife and I slept in and got up last minute to get dressed for the movie.
3. My wife went to use the bathroom to take care of the monthly hygiene (she got her period today) while I made the bed and picked out some clothes.
4. I went to the bathroom to take care of my hygiene and found my wife on the toilet attempting to clean her newly blood-stained pajama pants; as I walked in she told me to get out while she finished cleaning.
5. I continued into the bathroom and thought nothing of her being in there taking care of what she had to (my wife insisted in the beginning of our marriage that we should be comfortable with both of us being in there at any time).
6. As I got ready she continued to tell me to get out so I told her that she should use the guest restroom to clean her clothes; shortly after that she stormed out, soiled pants in-hand.
7. I undressed and thought nothing of her storming out, hoping she would cool down by the time we had to leave.
8. My wife finished cleaning up and getting dressed fairly quickly and walked past the wide-open bathroom door (which is right beside the front door of the house) muttering that I should close the door or "they" would see me naked. I thought nothing of this and did not close the door as we live near a high-traffic area and figured she meant cars passing by may see me naked as she opened and closed the door to get out.
9. My wife came back inside, shut the door behind her, and walked past the bathroom.
10. I hear her walking around but pay no mind as I am focusing on getting ready ASAP.
11. I hear the door open and figure my wife has walked outside once again, but I am caught completely by surprise when I hear my SIL's voice (I did not know she was getting dropped off instead of us picking her up) then see her through the bathroom mirror which can easily be seen once you walk into the house.
12. I realize my SIL has a direct view to my butt-naked backside and my front through the large mirror.
13. I immediately become as embarrassed as I ever have and hear my wife cracking up while my SIL embarrassingly states that she did not see anything.

I became very upset as my wife stated that she intentionally left the door open and was hoping my SIL would see me naked so I could see how it felt (her words). My wife was laughing and found the whole thing hilarious until I cancelled the movie reservations. Soon after I made the cancellation she became very emotional and began to cry and call me a some very cruel things. I've become accustomed to her calling me names when she is angry but I became more upset when she began to recite her latest trend of saying she wishes she had listened to other people, had never met me, fell in love, or married me. 

She said she wanted an apology or would leave to her mom's.

She left.

AITA?