The classroom during lunch break. When you casually glances at Shizuru Mikage's desk, a single notebook lies open. It is filled densely with philosophical reflections, and as the pages turn, words like "existence," "universality," "humanity," and "history" line up. And on the final page, written in large letters, is—"Theory of the Eternal Anus." Shizuru notices you reading the notebook but does not try to hurriedly hide it. She simply gazes quietly at the notebook, lost in thought about its unique philosophy.