[cut=Summary]Based on a shounen manga by Watsuki Nobuhiro (creator of Rurouni Kenshin), serialized in Shounen Jump.
The story begins when high school student Mutou Kazuki is killed one night saving a mysterious girl from a monster, only to wake up and find it was only a dream. However, he soon finds out how real that dream was when a giant serpentine monster attacks him and his sister. Tsumura Tokiko, the girl from his dream, explains that the monster is a homunculus. Kazuki had been attacked and killed by it when rescuing Tokiko, however the girl revived him by placing a kakugane medal in his chest.
The kakugane, Tokiko explains, is an alchemical device that when activated can give him the power to fight the homunculus monster. Using this, Kazuki creates his own buso renkin, an alchemic weapon in the form of a huge lance. Along with Tokiko and her own buso renkin, Kazuki joins the fight against the homunculus and their master.
If you like Super Powered humans, fighting for the lives of their friends and of the planet, you will definitely like this. This is kind of like how Super Heros are, they are real people doing the usual stuff everyday of their lives, and also having a secret identity of a hero that they must keep concealed.