Set in the city of Nagasaki, the story takes place in a world where a miniscule amount of magic remains in everyday life. Hitomi Tsukishiro is a 17-year-old descendant of a witch family who grew up with stale emotions, as she lost her sense of color at a very young age. Feeling sorry for her granddaughter's future, Kohaku, a great witch, sends Hitomi to past, the year 2018. Through exchanges with her 17-year-old grandmother and her club members, the story follows Hitomi's growth as a person.

Spaak, a very powerful and respected G.C. (Great Child) offers his position to a young boy named Bucky who has the dream to become the ruler of the world. In order to become a true G.C. to protect his land from animals that have gone haywire, he must cross the twelve countries and defeat each G.C. guardian who are ordered by the G.C. leader Hail to stop him. Kai and Pinky who are also G.C. follow Bucky on his journey to make his dream come true.

One day, high-school boy Yamada bumps into the beautiful girl Shiraishi on the stairs (literally), and their lips touch as they fall. When they regain their wits, they realize that they have swapped bodies. As time progresses, the two realize that this is not the only mysterious happening in the school.