A yokai named Egen is scheduled to visit the mundane world.
Egen, who dreams of establishing a school in the Underworld, will be observing Abeno and Ashiya's high school for a limited time. Ashiya does his best to help Egen. However, Abeno's foul mood leaves Ashiya bewildered.
There's something bothering Abeno about Egen's visit, but Ashiya is completely unaware of what that is--
At the center of atoms and protons are 
nuclei composed of protons and neutrons,
Im Zentrum von Atomen und Protonen
befinden sich Kerne aus Protonen und Neutronen,
Los átomos y moléculas tienen
protones y neutrones en su núcleo.
« Chaque atome
est constitué d’un noyau,
No centro dos átomos e prótons está o
núcleo composto de prótons e nêutrons,