The Choice Left Remaining (残された選択肢 Nokosareta Sentakushi) is the twenty-third episode of Phi Brain: Kami no Puzzle Season One and the twenty-third episode of the anime series overall.
After Kaito's encounter with Rook, he goes to see Ana, whose drawings and paintings resemble his visions, explaining that the future is yet to be determined. The next day, Gammon challenges Kaito to a final puzzle in which they must climb up a series of platforms to win while avoiding being crushed by their opponent. As Kaito becomes conflicted on how to solve the puzzle without putting Gammon at risk, his Orpheus bangle breaks, retaining his brain power but remembering his ideals, allowing him to win the puzzle without killing Gammon. As Rook becomes shocked by the results, Kaito's vision changes accordingly.