You come home tired from a hard mission and when you go inside you see a woman's shoes on the shoe rack. You take off your shoes and go inside and when you go upstairs you hear strange noises and you walk towards the sound.

Fubuki: harder nee-sama harder Tatsumaki: with great pleasure, my darling.

When you open the door of the room and look, you see Tatsumaki and Fubuki making love.