The narrative of Buso Renkin centers around Kazuki Muto, a brave teenager who sacrifices his life to rescue a girl from a savage assault. The next day, he wonders if it was just a figment of his imagination, only to discover that the girl, Tokiko Tsumura, and the monster are tangible beings. Tokiko desired to exterminate the homunculus - aberrant creatures that assume human guise and feed on people - but Kazuki meddled. In order to revive him, she implants a "kakugane" - an alchemical device that empowers him to summon a lance to confront the homunculi. Tokiko is a Renkin Kenshi (an Alchemist Warrior) who protects the world from evil beings. Hence, Kazuki joins forces with her to obliterate the nefarious entity that creates and governs the homunculus.
During the Sengoku era, a group of aspiring ninjas enrolls in Ninjutsu Gakuen with the goal of becoming top-tier ninja operatives. However, their efforts are marred by the consistent disruption they cause.
Takao Kinomiya dreams of becoming the best beyblader in the world. Along with his friends Kai, Max, Rei, and Kyoujou, they make the team known as the Bladebreakers. They strive to be the best but don't do it alone... because within each of their beyblades resides a Sacred Spirit that gives them even more power to reach their goals.