１００日の記念日 is a Weiß Schwarz card from PRカード【Wサイド】 Khb/W102-112. Compare listings from Singapore Weiß Schwarz sellers on CardJio, then jio them on WhatsApp.
Choose 1 of your opponent's level 1 or higher characters, your opponent chooses 1 level X or lower character in their waiting room, and exchanges them. X is equal to the level of the character you chose -1.