Magical Sempai

The narrator tells us that today is Banc's second birthday, and that he has a message for his friend, sempai. He asks her if she would like a cake for her birthday. She says no, and the narrator says he's going to do some "magic tricks" on her. First, he takes a picture of a cake and uses the same technique as he used on the murder scene to transform it into a three-layer cake. Then he takes the picture of the cake and replaces it with a four-layer one hidden in the sleeve of his shirt. The narrator says it's been a long time since he'd done such a thing, but now that he does it, he can't believe how much he has grown.