Sky Walk

is the ninth episode of the No Game No Life (Series) anime series. It first aired in Japan on June 4, 2014 on AT-X, and later on June 6, 2014 on other networks.

Plot summary
In an attempt to remember her brother, Shiro frantically searches the castle to find Sora. To her dismay, she is unable to find Sora, and begin to doubt he even exists. Stephanie and Jibril are unable to recall whom Sora even is, and are unable to help Shiro in her search. Believing Sora is truly a phantom of Shiro's imagination, Jibril challenges Shiro to a game of chess, where the wager is Shiro's memories of Sora. Jibril asks Shiro to lose this game on purpose, so that she can put her mind at ease about Sora.

As Shiro is about to lose against Jibril, she detects a faint feeling from Sora. This inspires Shiro to win the match, instead of throwing the match against Jibril. To prove that Sora exists, Shiro asks Stephanie and Jibril to recall the previous few days, in which all both are unable to do. After asking Jibril to use her ability to detect magic in the area where she was found sleeping, Shiro beings to piece things together. Stephanie trips in the room, and Shiro notices three unused Othello pieces. Shiro then remembers why she and the others were unable to remember Sora.

In the previous two days, Sora had entered into a battle of against Chlammy Zell, in a special game of Othello, modified by the magic of Fiel Nirvalen. The wager for winning the game was the ability to gain two demands from the opposing player. In this game of Othello, memories would be robbed from the current losing player, and given to the current winning player. However, the lost of memories would also weaken the player themselves, and potentially kill the other player, if too many of their memories were lost. For this reason, Sora asks that if such a thing would happen, another friend of the player would be able to step in and play for them. Sora purposely began to lose his memories, so that Chlammy would believe him in the fact that he was not in alliance with any other nation (during their previous game for the rights to be king), and furthermore, reveal his plans to Chlammy to take over the Eastern Union. In the process, he began to lose himself, and depended on Shiro to finish his game of Othello. Shiro finishes and wins the game of Othello for Sora, thus revealing all characters in the room.

Upon recovering consciousness, Sora then begins tell his two demands for winning the game. First, he demands that each keeps a copy of the memories they stole from one another, while keeping their own original memories. Second, he demands the ability to alter Fiel's memories.

Characters
The following characters are listed by the order which they appear in.

Major characters

 * Shiro
 * Sora
 * Stephanie Dola
 * Jibril
 * Chlammy Zell
 * Fiel Nirvalen

Minor characters

 * Non-speaking roles
 * Shiro's Mother
 * Sora's Father
 * Hatsuse Izuna

Events

 * Flashback of Shiro's memory from age 0-3
 * Shiro goes mad from Sora's disappearance
 * Stephanie and Jibril believe Shiro had false memories inserted by Izuna
 * Jibril plays chess with Shiro, hoping to erase her supposedly false memories
 * The girls raised the possibility that Sora does actually exist and that there was a game still ongoing
 * Flashback of how the game was set up
 * Shiro winning the game and reuniting with Sora
 * Sora issued his two requests to Chlammy and Fiel

Key differences from light novel
In the light novel,
 * There was further discussion about the limitations of the Ten Pledges where each character was asked to 'become' another character after losing a game. This was in Light Novel Volume 3: Prologue, Part 2, which was skipped in the anime.
 * Scenes of Sora playing against Chlammy were interlocked with the scenes of Shiro searching for Sora from the start. In the anime, the scene of Sora and Chlammy's game only appears after Shiro loses consciousness.
 * Stephanie was the one who first discovered the possibility that they were in the middle of a game, whereas in the anime, it was Shiro who did so.
 * Jibril confirmed Sora's existences by contacting Hatsuse Ino, acknowledged and requested for punishment for the guilt of suggesting the removal of those "false" memory from Shiro, and expressed anger toward the one who caused the situation. These are skipped in anime.
 * Shiro did not actually hear Sora calling her out to hold him so he does not go insane. Sora however, does experience the presence of Shiro, Stephanie and Jibril by his side, who, from his point of view, react to his words..
 * Shiro figured out how the game would progress by using Sora's usual habit which is not shown in the anime.
 * There are a number of scenes reflecting Chlammy's individual reactions to each of Sora's memories, which did not appear in the anime.
 * Chlammy and Fiel were discussing how the game was biased toward the one who designed the game, whereas this was skipped in the anime.
 * There was a special rule that you have to place your piece even if you cannot reverse any of your opponent's pieces, which is not mentioned in the anime.
 * Only Sora, Shiro and Chlammy were crying after the game. In the anime, Fiel was also crying with them.
 * Shiro's conversation with Jibril and Stephanie about their mutual past as the two remember it as well as the game of chess between Shiro and Jibril is held through the tablet, not via direct interaction.

Trivia

 * The episode is in black-and-white from the point when Shiro falls into despair to the point when she realizes Kuhaku must never lose (in her chess game against Jibril)