A Pact Concealed Within a Maze (迷宮にひそむ契約 Meikyū ni Hisomu Keiyaku) is the first episode of Phi Brain: Kami no Puzzle Season One and the first episode of the anime series overall.
Kaito Daimon, a genius at solving puzzles, is given a strange device and an invite to solve a dangerous puzzle inside a ruin. Going with his friend, Nonoha Itou, he makes his way through the strange maze, and manages to find a secret solution thanks to Nonoha's help. Arriving at the center of the maze, Kaito finds a strange bangle, known as the Armband of Orpheus, which attaches itself to his arm. After this happens, the room they are in is sealed off, and Kaito is given a puzzle in which he is told to pull a correct lever to stop the pillars holding the ceiling up from breaking apart. As Kaito reaches wit's end, the bangle on his arm glows and Kaito enters a state where he's able to see the puzzle's solution.
Kaito is seen with Okudera, the "Puzzle King", walking inside the first Sage Puzzle. He saves the man when he thought he had reached the treasure of the puzzle, which almost killed him had Kaito not pulled him out of the way and when Okudera began to complain about not getting the treasure, Kaito wonders if the treasure was worth his life. When looking at the damage the puzzle did outside, he mumbles, "Puzzles don't endanger lives.".
He is seen again on the Root Gakuen Highschool field oval laying down desks in the same maze as the Sage Puzzle last night. He blocks off Takeda and his friend from the solution - which they berate him for after he tells them there is no solution. He removes a gadget from his pocket that revealed the map for the Sage Puzzle and he wondered why he was given it. Nonoha shows up and kicks him to the ground, afterward, grabbed his head in a headlock, demanding that he return the desks.
He and Nonoha are seen walking down the school's hallways heading towards the Puzzle Club. Nonoha tries to persuade him out of going, saying that he'll only get into a fight. Kaito didn't seem to understand what she was talking about until she reiterated that he told the president of the club, Souji Jikukawa, that his club wasn't good enough when Souji gave Kaito an invitation to join. Kaito simply agreed and stated it was the truth.
He walks into the puzzle club, greeted by a girl at the front, and asks if the president was in. She gave a negative and Kaito said he'd wait for him. While he was waiting in the next room, Takeda and his friend walk in, Takeda wondering if Kaito would like to do a Sudoku to forget the puzzle he created that morning. He explained how to do Sudoku and Takeda's friend said it took Takeda himself a whole day to finish the puzzle. Kaito finished it in about a minute. The girl who greeted him praised his abilities, while Nonoha seemed shocked into disbelief.
Souji then walks into the room, greeting Kaito and asking if he finally decided to join the Puzzle Club, to which Kaito bluntly denies. He pulls out the gadget and asks Souji what it was - since Souji was the one to give it to him.
It goes into a flashback of when Kaito had been using the gadget and solving the puzzles that were sent to it. After solving twenty in a row - he got a invitation by a user, "Minotaur".
To Souji, he states that the designated location was the Sage Puzzle ruins he was at last night, to which Nonoha asked if he was the high-schooler that saved the "Puzzle King". Kaito agrees, but argues that he's just a third-rate puzzler. He asks Souji what the gadget meant. Souji states that he's getting free puzzles sent to that thing, but Kaito interrupts, saying it wasn't about the puzzles. Souji reiterates that he doesn't have to solve puzzles, he can quit, but a ringing from the gadget interrupts them. Kaito opens it up to reveal a invitation from the "Minotaur" which goes to a video feed of the man, saying that to accept his invitation and go to the Sage Puzzle ruins in the mountains. If he wins; he'll get a treasure. If he loses; he'll die. Nonoha is outraged, wondering why he would die. Souji asks if Kaito isn't interested, but Kaito just closes the device, saying, that there was no puzzle he couldn't solve. He then pulls down the bottom of his right eye and sticks out his tongue, leaning forward. Souji laughs, "Einstein.".
Kaito and Nonoha arrive at the Sage Puzzle ruins that have been blocked off by security tape. Nonoha wonders if Kaito is really going to do it, when getting an affirmative, reiterates that he stated it was deadly. Kaito responds that that was why he was going, he couldn't just sit around knowing that the "trash" who made it are still out there, saying he'll solve the unsolvable puzzle. When Nonoha questioned why he was so determined, Kaito said it was a promise.
A boy stated that Kaito needed to save those "unhappy" puzzles by solving them; making them free.
A white-haired boy praises Kaito on his puzzle skills.
Kaito stated that Nonoha should go home when she was pondering his statement to which see immediately denied, saying, that she "needed to keep an eye on you [him]".
When they are seen walking into the puzzle, Nonoha trailed in that she could protect herself, Kaito told her to do what she liked in that case. "Minotaur" appeared on a rock ledge when they walked farther in, welcoming them. Kaito questioned his identity, to which he replied that he was their overseer. He begins to explain that the Sage Puzzle is a barrier with a treasure hidden behind it. Kaito doesn't care about the treasure; he just wants to solve the unsolvable puzzle. "Minotaur" fades into the rocks. Nonoha asks what they were going to do, Kaito responds that "It's puzzle time!"
They run into the maze and come across their first puzzle, which Kaito easily solves. Kaito states, after they walk through the door the puzzle opened, that they were at the entrance. When Nonoha questions what they were going to do if he stated there was no solution earlier, he responds by pointing to a dead end the map on his gadget produced and saying that he wanted to go there, but he doesn't know why. Nonoha tell him to leave it to her and darts off, startling Kaito. She keeps her left hand grazing the wall, stating that she read on the net that if you keep your hand on the wall, you'll always find the exit. Kaito questions that. When Nonoha begins to go faster, Kaito begins to lag behind.
When Nonoha turns a corner, a trap door suddenly opens below her, making her scramble to grab the edge - which she can't. Kaito runs after her, jumping over the door, lashing his hand out to grab hers and flips over the door, slamming his back into the other side.
They begin to walk back, Kaito telling Nonoha not to run off on her own. He stated that he couldn't remember how to get back, or where they were. Nonoha leaded them back instead.
They arrived at the dead end and Nonoha comments that it looks different - that the support beams were always inside the rails, there they were outside. Kaito asks her if she saw an axe decoration nearby. She pointed to a corner support beam. Kaito examines it, then pulls it out, making the wall near Nonoha slide out and begin to move. The blank space on Kaito's gadget became filled and they continued to walk. The two reach the end and open the large door, revealing a large line of stairs and a temple at the top, which "Minotaur" states Kaito has to go up alone. He does; with Nonoha yelling at him for it. Inside the temple, holds a Mandala, which Kaito touches with his left hand. The moment he does, the lines begin to glow and wrap around his arm, forming a band. Several ornaments slide themselves up his arm and connect before he hit the ground in surprise. Nonoha called after him. "Minotaur" claims that Orpheus' Contract has been fulfilled and to use his brain to its limits in order to solve the next puzzle and if he failed, the ruins would collapse on him and Nonoha.
Slowly, it revealed a complex puzzle of wood and gears that Kaito had to solve. As water began to fill it, Kaito being warned that the puzzle would break apart before long, several planks broke off, landing near Nonoha, forcing Kaito to think faster, causing himself into an almost panic-state. When Nonoha calls him out, he yells, activating Orpheus, the ornament on his arm. It began to glow. As Kaito began to concentrate, he opens his eyes, and his right is revealed to be glowing red.
- Kaito Daimon
- Nonoha Itou
- Naoki Takeda
- Yuuichi Aizawa
- Souji Jikukawa
- Tamaki Chieno
- Baron Kaido