It all started at that shrine...
Sugano Fuu is a 1st year student who goes to Tsukiyado High School. One day along with her upperclassman Norizuki and her classmate Hirose they decided to investigate the "Seven Mysteries of Tsukiyado" as part of their club activities.
It wasn't a particularly interesting topic to find information on, they were just wasting time. "Ah, There's a weird shrine at our school isn't there. Why don't we go investigate?" In that kind of noncommittal fashion they went to look into it.
At the shrine Hamura and Kuga were waiting. They weren't really on good terms with those two, they were more like complete strangers. With a quick greeting the investigation started.
The shrine was pretty old and even though it wasn't locked the door wouldn't open. It seemed like it was rusted shut, when they tried to pry the doors open they quickly crumbled. Within that dirty rubble they saw "something". As they blankly gazed at that "something" suddenly smoke started pouring out.
"What if it's poison gas!!"
With all their might they threw the "something" as far away as they could. But after all that they were still enveloped in the smoke coming from that "something". And before they knew it they were transformed into frogs.