Imamiya Satoshi, "Sasshi" to his friends, has grown up in the Abenobashi Shopping Arcade in Osaka, along with his childhood friend, Asahina Arumi. Now, all that was stable in his life is in ruins. His family's bath house has closed and been torn down, and Arumi's family is moving to Hokkaido - and taking her with them. In the midst of all this, something happens to the framework of reality, and Sasshi and Arumi slip into a weird parallel world. It's still Abenobashi, but not their Abenobashi. Strange things are afoot, and Sasshi must find out their meaning, in order to reach a goal that he barely understands.
Arumi and Sasshi attempt to get back to their own Abenobashi, but willy-nilly find themselves traversing a series of apparently nonsensical worlds based on genres including science fiction, war, fantasy, dating sim games, and even American movie genres such as film noir. Their quest to return home is at core a Bildungsroman because the Abenobashi dimensions are mostly hobby worlds of increasing sophistication. Not only does each alternate Abenobashi manifest Sasshi's otaku fetishes in surreal fashion, they are peopled by surreal analogs of Arumi and Sashi's relatives and acquaintances. They also repeatedly encounter a mysterious blue-haired stranger who is eventually revealed to be the man who developed the shopping arcade itself decades before: the legendary onmyoji mystic Abe no Seimei.