That Mysterious World... / That Guardian of Aqua...
S2:E22
2006
IMDb
When Akari innocently suggests that perhaps the little space between two stairs at the Aria Company is a portal to another world, President Aria, ever curious, squeezes through the gap, and pops out on the other side to find a terrifying sight! The second story is a flashback to when Akatsuki was little. He considered himself to be a superhero, but he wasn't quite as heroic as his imagination led him to believe...