Kyouko used her Soul Gem to briefly end up in Sayaka's body, which was empty since Sayaka's Gem turned into a Grief Seed, whereupon she discovered Sayaka hadn't eaten in a while, so she bought food to feed her body with, after which... well, apparently the junk food didn't agree with Sayaka's system, necessating a trip to the bathroom and the subsequent handling by Kyouko of her naughty bits, and now she's giving Kyouko grief in the afterlife for that.
trembleYou... you have to take responsibility for that!!Well, I... um...bluuuuush...... I'll be in your care, then.tremble~ In the afterlife ~