Season 1 : Supersonic monkeys, vampires, talking fishmen, and all sorts of different supernatural monsters living alongside humans—this has been part of daily life in Hellsalem's Lot, formerly known as New York City, for some time now. When a gateway between Earth and the Beyond opened three years ago, New Yorkers and creatures from the other dimension alike were trapped in an impenetrable bubble and were forced to live together. Libra is a secret organization composed of eccentrics and superhumans, tasked with keeping order in the city and making sure that chaos doesn't spread to the rest of the world.

Pursuing photography as a hobby, Leonardo Watch is living a normal life with his parents and sister. But when he obtains the "All-seeing Eyes of the Gods" at the expense of his sister's eyesight, he goes to Hellsalem's Lot in order to help her by finding answers about the mysterious powers he received. He soon runs into Libra, and when Leo unexpectedly joins their ranks, he gets more than what he bargained for. Kekkai Sensen follows Leo's misadventures in the strangest place on Earth with his equally strange comrades—as the ordinary boy unwittingly sees his life take a turn for the extraordinary.

Season 2 : Three years ago, a gateway between Earth and the Beyond opened in New York City, trapping extradimensional creatures and humans alike in an impermeable bubble. After the city's restoration, monsters, magic, and madness are common findings in the area now known as Hellsalem's Lot. Leonardo Watch, a young photographer who unwillingly obtained the "All-seeing Eyes of the Gods" in exchange for his sister's eyesight, came to this paranormal city to find answers to the mysterious power that he possesses. He later finds his life drastically changed when he joins Libra, a secret organization of people with supernatural abilities dedicated to maintaining order in the everyday chaos of Hellsalem's Lot. 

However, this is only the beginning of Leonardo's unexpected journey ahead. Regardless of the constant threat of otherworldly enemies, he is determined to uncover the secrets of his power and find a way to restore his sister's eyesight. Kekkai Sensen & Beyond follows Leonardo as he sets off on more crazy adventures with his comrades, fighting to ensure peace and order.