Oh, Mami-san, you're so erotic! And Nagisa-chan, you're a good imouto! I love how she's yelling about the importance of giving Mami the space to be with OL-san, only to later see her eating with Tatsuya.
Oh, and OL-san, you're so wonderfully perverted- having Mami-san first engage in bloomers sex, then having sex with her in her Magical Girl form. Still, congratulations on your's and Mami's engagement.
So, am I to understand that Mami somehow turned into the "Christmas Witch" at the end?