Amu Hinamori and the Seiyo Elementary Guardians continue their quest to seek out and purify X Eggs while in pursuit of the elusive Embryo—an egg said to be able to grant any wish. However, the Guardians must secure the Embryo before it falls into the hands of the nefarious Easter Corporation. As part of their plan to lure out the Embryo, Easter hires Lulu de Morcerf, an aloof girl whose ruby necklace gives her the ability to convert Heart Eggs into Mystery Eggs. These strange Mystery Eggs cannot be purified as easily as X Eggs, and they can force its owner to undergo a Character Transformation. With this growing threat, the Guardians must track down its source and put a stop to them before the matter gets out of hand. Facing insurmountable pressure from these two new objectives, will the Guardians be able to recover the Embryo while also dealing with the Mystery Eggs?

Her name is Mary Saotome—she is brazen, insolent, and defiant, yet highly intelligent. Upon transferring to Hyakkaou Private Academy, where a student's worth is determined by their wits through gambling, she seizes a glorious win against a classmate and immediately captures the attention of the devious student council members. With the bottom of Hyakkaou's rigorous hierarchy determined by least gambling winnings, the future for Tsuzura Hanatemari looks grim. As Tsuzura's childhood friend, Mary resolves to rise through the ranks and secure enough money to free Tsuzura from the shackles of the unjust system. Mary's perseverance and refusal to lose drive her to surpass and humiliate even the strongest opponents, but certain student council members seem to have greater plans for her.

Lü Shu is a frail teenager with an iron will. After losing his parents, he enrolls in a prestigious high school while working for a living and looking after his adoptive sister, Lü Xiaoyu. However, Lü Shu's quiet life abruptly changes when a car accident awakens his latent cultivation superpowers. Now cured of his physical weakness, he decides to hide his newfound abilities, as the art of cultivation is still shrouded in mystery—and the fate of cultivators uncertain. Meanwhile, Tian Luo Di Wang, the international foundation responsible for monitoring the cultivators, sets its plans in motion. Under the impetus of their member Xi Fei, a special cultivation training group is established in Lü Shu's high school. Although Lü Shu is forced to join the program, he is determined to hide the nature of his fearsome power, for his cultivation draws from an unlimited resource: the negative emotions of others brought about by his actions.

Kaoru Hanabishi, a college student who lives alone, met a beautiful but bewildered girl dressed in a kimono at a train station. He volunteered to guide her way to the address she was looking for, which happened to be in his neighborhood, but turned out to be an empty lot. Not knowing what to do next, Kaoru invited the devastated girl to his apartment and asked for any additional clues to her destination. She supplied him with a photo of two children whom Kaoru immediately identified as himself and Aoi Sakuraba, his childhood friend. It turned out that the girl in front of him is Aoi Sakuraba herself, his betrothed fiancee who came all the way to Tokyo to marry him. Her revelation was not only surprising but also reminded the deepest part of Kaoru's memory for why he left the Hanabishi family in the first place.