* Before the fight with Eastern Federation starts, Kurami and the elf Fiel (Fii) decides to confront [ ] in order to force them to stop.
* The game they decided to play was a version of Reversi played with memories instead of normal pieces.
* The game board took a day to be built by Fii and Jibril, that's why we went from day 19 to day 21.
* The memory pieces that are "eaten" are taken over by the opponent, this means that either Kurami or Sora could end up with the other memories/existence.
* While the game takes place the companions will stay in a world created through the magic of the game.
* According to the rules established, once someone existence gets "eaten" and the situation arrived that the companions forgot, then the game is over. Once the game is over, the one who has the most pieces wins.
* The tips Sora gave Shiro were in order for Shiro to end up winning the game, after Sora bring Kurami and Fii to help them winning the game against the Eastern Federation (how will they help? well that's a story for another time )