Phi Brain: Kami no Puzzle 2

Also known as:  Phi Φ Brain: Kami no Puzzle 2, Phi Brain: Puzzle of God 2, Phi Brain: God's Puzzle 2, PhiBrain 2

The 2nd season of TV anime series Phi Brain is once again created by studio Sunrise, continuing the original "school adventure" story about a high school boy named Kaito who loves puzzles. In the second season, the story continues to revolve around the Orpheus bangle and Phi Brain, but the puzzle battles heat up. A new enemy, a group of boys named Orpheus Order, appears before Kaito and the others, and the battles begin anew. (based on ANN synopsis)

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Producers, official website and other details: AniDB, ANN, Wiki