The story tells the tale of Semi, a bright girl who goes in a magical time journey with the genius teacher Wai, in order to prevent the evil X from utilizing the powers of the magic cube for evil. Along the way, Semi and her math school friends run into history and math problems that they must solve with logic and wit.

In the world of Mushrambo, human life has all but come to an end. After a deadly virus threatened the extinction of mankind, a new race called the Enterrans was created to preserve life on Earth. However, relations between the Enterrans and their creators did not remain peaceful. Soon a war broke out with the Enterrans fighting against the humans and their robots. Ultimately the Enterrans were the victors of this conflict, renaming Earth as Enterra in honor of their victory. Before the last vestiges of humanity fell, one of the few remaining scientists put his daughter, Yakumo Shindou, into a sleep chamber. His hope was that his daughter would one day reawaken and find the human sanctuary known as Shinzo, reviving humanity and restoring peace between humans and Enterrans. Centuries have passed since the war; Yakumo now awakens and meets an Enterran named Mashura who pledges to assist in her quest. Also joined by the Enterrans Sago and Kutal, the group must now work to locate Yakumo's missing memories and locate Shinzo. But not every Enterran is as kind as Yakumo's new friends and some are prepared to commit any atrocity to prevent the return of humanity.

Momona is an ordinary junior-high school student hailing from Jewel Land. At her cousin's wedding, she envies the bride, Lady Diana, due to the fact that she is marrying the cousin who she had a slight crush on. However, once she sees Lady Diana and her cousin together, Momona begins to like her, and accepts her as her cousin's bride. Just as Lady Diana is about to properly meet her and introduce herself, Momona is transported to a snowy place in Jewel Land where the ruler, Lady Jewel, is giving a speech to the Petit Ladies, girls who are chosen as Jewel Candidates to be the next Lady Jewel. Momona meets her partner and mentor, Ruby, a white rabbit, who will guide her through the tasks in becoming Lady Jewel. Whoever passes the most tasks wins and becomes the next Lady Jewel, but standing in her way is Lillian, a girl who also aims to win the title of Lady Jewel, so she can choose her brother, Cayenne, to be her King alongside her. Momona soon also begins to fall in love with Cayenne, yet Lillian doesn't want her to get too close to him. Cayenne also seems to harbor feelings for Momona, but who will be chosen in the end as Lady Jewel to decide it all? And will Momona and Lillian ever become true friends and will Cayenne and Momona ever be together?