A story about mahjong.

The anime centers around a boy named Kouta Kouka (Kouka Kouta in Japanese name order, an apparent wordplay on Coca-Cola). Kouta strives to be the world's best Bottle King at the Bottle Battles in the virtual Drink World. He comes across his Bottleman partner Colamaru and then wages battles with various rivals. (Source: ANN)

Mysterious cards came down from the sky one day. Capable of summoning powerful creatures from another dimension, they became the centerpiece of a new game called Bakugan. The game gained instant popularity among children and teenagers, with the best of them competing in a worldwide ranking. Meanwhile, war for domination over Vestroia, the homeland of Bakugan cards, rages on. Invaded by the White Dragon Naga and his servants, the Doom Beings, the realm becomes increasingly destabilized. Dimensions begin to merge and many Bakugan players come to realize that their pastime is not merely a game. Danma Kuusou, one such Bakugan player, intends to become the World Ranking's leader someday. However, during one of his fights he experiences a vision of a clash in Vestroia. The fight suddenly moves to Earth, where Danma comes into possession of a talking, mighty fire Bakugan, Pyrus Dragonoid. He soon gets dragged into the conflict, and together with his Bakugan Brawlers team, must traverse the dimensions and restore balance in a ravaged world. [Written by MAL Rewrite]

The franchise's story centers on wizards who gather mazica in order to save the world. Junior high school student Kezuru wakes up after a strange dream featuring himself as a wizard, a creature called "mazin," and a mysterious girl. The next day, his friend Kuracchi proudly shows off the newly launched Mazica Party card game. To Kezuru's shock, all the characters drawn in the game's cards are just like the ones in his dream. Meanwhile, Kezuru receives a notification for an event at the major international company Mazica. Intrigued, Kezuru goes to the Mazica Store as directed, only to meet the Mazica CEO himself, Jeff Johns. Johns says, "I have great expectations for you," and hands Kezuru Mazica Gear. On his way back home, Kezuru is attacked by an airship-like creature. Just when he thinks, "this is it!" to himself, his Mazica Gear erupts and a magic book appears. When he scratches a card, he seals a contract with Barunya, a "mazin" creature that is an odd remixed fusion between an airship and a cat. The mysterious girl Anya says Kezuru and those of his ilk will be "the true wizards who save the world." Amid all these mysterious revelations, Kezuru enrolls in the Mazica Academy and engages in Mazica Party card battles alongside his partner mazin. (Source: ANN)