Many Japanese students are familiar with the legends of the seven school mysteries. Not every school has them, of course, but everyone knows someone who goes somewhere that has them. Largely obscure and unfounded, these legends are passed down as stories from student to student. Some mysteries are harmless, in fact, they may even be considered blessings. These tales usually involve good fortune with romance or academics. Others are more ominous, typically warning students of disappearances or injury, occasionally leading up to their untimely demise.

Kaibara High School was once such school without any mystery. No good, no bad, no creepy, or even silly. Students roamed the halls free of any such fantasy. And it was strange, of course, because that would lead people to believe that another school in the vicinity would hold such rumors. The truth is, not a single school in all of the area had a single school mystery.

So what legends did exist, you might be wondering? Well, it's rather peculiar, but instead of several handfuls of schools having their own seven mysteries, it would seem that the entire town had been shrouded in one giant mystery. And so, as if to make up lost ground, the town had not seven, but thirteen mysteries. Each one intertwined and becoming more and more complex. No one has ever encountered all thirteen mysteries and lived to see the end of it. Nothing bad happened to them, it's just that so much time had passed before all the pieces came together that those involved simply were unable to connect all the dots, or they simply passed away.

However, for the first time in nearly thirty years, the legends were increasing in their popularity. It would seem that they've grown restless and have been desperately calling out for someone to come and find them. For, you see, these particular mysteries can indeed be solved and laid to rest, if only someone cared enough to try. And that's where this story begins. In a clearing, in a rather dense set of woods, there's a young high school girl who has just encountered one of the thirteen mysteries.

Kaibara High School's second year, Miss Tohru Honda, has unintentionally stumbled across the legend known as the Year of the Dog.