After saving the world from the destructive might of Majin Buu, Gokuu Son and his allies look forward to a well-earned rest. However, unbeknownst to them, their battle was recorded and observed by Gomah, an evil being who assumes the title of King in the Demon Realm, filling the void left behind with the death of former ruler Dabura. At Gomah's side is Degesu, the younger brother of Higashi no Kaioshin, a being who lords over the universe. Jealous of his brother's power, Degesu works alongside Gomah to steal Earth's Dragon Balls and preemptively subdue any potential future enemies. Calling upon the power of the legendary dragon Shenron, Gomah wishes for Gokuu and his friends to be reverted into children, intending to rob them of the limitless power that defeated Buu. With Earth's greatest warriors shrunken down, Gomah abducts Dende, the planet's acting god. But Gokuu refuses to be set back by his new body, working to master his younger form to fight as proficiently as he could as an adult. Joined by Kaioshin and Glorio—a mysterious but seemingly rebellious demon—Gokuu pursues Gomah to the Demon Realm in order to rescue Dende and restore his friends to their natural ages.

Second year high school student Koguma doesn't lead a very interesting life. She has no parents, and no friends nor hobbies to keep her daily life busy. One day, she acquires a second-hand Honda Super Cub motorcycle and rides it to school. As time goes by, not only does Koguma have a new adventurous life, but she also forges precious friendships thanks to her precious little motorcycle.

Ever since childhood, Scarlet El Vandimion has preferred to deal with wrongdoers by using her fists. However, to preserve her family's image, she suppresses her instincts and tolerates the abuse inflicted by her childish fiancé, Second Prince Kyle Von Pallistan. Only Kyle's brother, First Prince Julius, is aware that there is more to Scarlet than meets the eye, but she cares little about his growing interest. In the middle of a ball, Kyle accuses Scarlet of harassing Terenezza Hopkins, a commoner that has taken his heart. Scarlet's engagement to Kyle is nullified, leaving her outraged that all of her efforts to endure thus far have amounted to nothing. Scarlet dons her studded leather gloves, once again becoming the "Mad Dog Princess." Joined by Julius and werebeast Nanaka, Scarlet is ready to give filthy nobles a taste of their own medicine—one punch at a time.

While walking home, Mikiya Kokutou comes across a familiar sight: Shiki Ryougi standing by a railing amidst the falling snow, just as when he first met her four years ago. While the two talk of their past and shared experiences, Mikiya realizes that something is strange about Shiki; rather, this is not the woman he has come to know, but an entirely different entity that dwells within Shiki's body...