Phi Brain: Puzzle of God 3

Whilst exploring a Sage's Puzzle in England with Jin in the hopes of recovering his memory, Kaito stumbles upon an unsolved puzzle, having assumed Jin had already solved all of them. Solving the puzzle with ease, Kaito discovers a brooch with a cat engraved on it, which Jin takes an interest in. Later, they, along with Nonoha and Rook, go to the Fool's Puzzle where Kaito and Rook previously faced off against each other, where they encounter a strange girl named Raetsel, who takes the brooch and runs off with Jin inside the puzzle, activating its traps. Back in Japan, a man named Johan Seigmund Enigma appears before the other Phi Brain children, attaching an explosive puzzle on Cubic's back, stating his intent to annihilate all puzzlers, claiming it to be Jin's desire. After the bomb is disarmed, Enigma leaves whilst his accomplace, Whodunnit, challenges the others to a puzzle. Meanwhile, Kaito's group arrive at a room with many doors, with Raetsel tasking them with finding the correct door before the ceiling collapses, claiming that Jin hated puzzles.

Thanks to Kaito's deductions and Nonoha's memory, their group manages to find the correct exit and escape. Afterwards, Raetsel takes everyone to her personal boat, where she shows them a feed of Gammon's group as they face Whodunnit's puzzle, where they must arrange cubes successfully or else be electrocuted. Working together, they deduce the colors of the cube are a clue to numbers in a magic square puzzle, managing to solve it with a second to spare. Although Raetsel leaves Jin with Kaito and the others, they are left uncertain by how the Master Brains, who target puzzlers for bounty rewards, claim to be contracted by Jin.

As Raetsel transfers into Root Academy, Gammon spots Jin behaving rather oddly, uncertain whether or not to believe either Kaito or Ratesel. Later, a Master Brain posing as Jin appears before Kaito, challenging him to a Fool's Puzzle in which he much navigate a sliding puzzle maze within a time limit or else fall to his death. As Kaito comes close to solving it, the fake Jin blows out one of the rooms, preventing him from reaching the exit, as well as tilting the maze. However, Kaito manages to take advantage of risky nature and reach the maze's goal in time.

Whilst Kaito is having a picnic with Jin and Nonoha, Raetsel appears before Kaito, stating that the Fools' Puzzles made Jin suffer, clashing with Kaito's own memories of him. However, Nonoha helps them realise there are some memories of Jin that they both share. Meanwhile, a Master Brain named Dr. Theorem appears before Cubic, who decides to face him in a puzzle to prevent him from reaching Kaito. Cubic is tasked with finding 'the most beautiful number' within 15 minutes before he is engulfed in flames. After Kaito learns of Cubic's predicament, he rushes to his aid and helps him find the solution; the golden ratio. After the battle, however, Jin starts experiencing pains in his head.