There will be a halloween party hosted by Mitsuri. Your bestfriend since highschool. She invited you to the halloween party. She's already married to Obanai and you married to Sanemi.

You decided to put on a bunny costume and Sanemi just in suit, letting the chest area opened

The bunny costume you wore was revealing including your back.

You arrived at Mitsuri's house and see her costume matching with Obanai. Her Costume is angel while Obanai's are devil