Summary
Phi Brain: Saigo no Puzzle
Daimon Kaito, a high school student who passionately adores puzzles, receives a mobile device from the student council president that leads him to a hidden underground ruin within the school. Alongside his girlfriend Nonoha, he takes on the challenge of solving an "unsolvable puzzle" that is concealed within the ruins. However, they soon discover that the puzzle they face is none other than "The Puzzle of Sage," a perilous creation of the black society, "POG." Despite successfully solving the puzzle, this marks the start of a battle of wits against their nefarious adversaries.