Kaito Daimon is an exceptional high school student with an extraordinary talent for solving puzzles. His intelligence allows him to suspect that any test he takes is designed to evaluate his unique ability. Unfortunately, Kaito finds himself in a deadly situation when POG, a sinister group of murderers, sets up a lethal Philosophers Puzzle. The puzzle consists of traps and challenges where failing to solve the secret correctly will result in death. However, Kaitos skills prove useful as he passes the first test, saving both himself and his childhood friend Nanoha. As a Solver designated by POG, Kaito is now required to travel the world with other Solvers, attempting to unravel the latest deadly riddles left behind by the group. Each new conundrum poses a threat of death, but once presented with a puzzle, Kaito's intelligence allows him to unfold, unravel and unlock it.