Welcome to the Queen's Kingdom (迷宮にひそむ契約 Meikyū ni Hisomu Keiyaku) is the tenth episode of Phi Brain: Kami no Puzzle Season One and the tenth episode of the anime series overall.
As Kaito dreams of appearing on a TV puzzle show hosted by Elena "Antoinette" Himekawa, Gammon, who had been Elena, jumps in to protect her when it looks like she is being cornered, though she is not too happy about the rescue. As a POG Giver, Elena is asked by the headquarters president to bring Kaito, Gammon and Nonoha to a Kenja Puzzle. They are trapped in a puzzle suspended over a pit in which Kaito is given the option to sacrifice his friends to receive hints, while Gammon and Nonoha are given the option to either sacrifice themselves, or make Kaito fall instead. As Elena tempts the others to sacrifice Kaito, she is surprised about how much faith they have in Kaito. As Kaito struggles near the end, the Orpheus Bangle kicks in and he manages to solve the puzzle just in time.