Mayu's Room

Mayu's Room (繭の部屋) is the collective name for the set of rules that restrict the use of cards in tournaments for the purposes of game balance. These rules only officially apply to official tournaments; casual meetings and unofficial tournaments are not required to have these restrictions in place, although they can adopt these rules if they so wish.

Simultaneous Use Restriction
These rules were announced on August 8, 2014 and went into effect on August 28, 2014. You may not have both cards from these pairs in your deck. It does not matter how many of each card you put in. For example, if you have 1 Osaki, you may not put Repair or THREE OUT in your deck. If you have 4 Osakis, you may not put Repair or THREE OUT in your deck.
 * Osaki, Phantom Beast Deity and Repair
 * Osaki, Phantom Beast Deity and THREE OUT

You may still put Repair and THREE OUT in the same deck.

Restriction to 2
These rules were announced on March 20, 2015 and went into effect on April 25, 2015. You may only have two or less copies of the following cards in your deck. You may not have three or mroe copies of these cards in your deck.
 * Valkyrie, Unforgettable Fantasy
 * Repair
 * Arcgain, Archangel of Pioneering