Buso Renkin (武装錬金, Busō Renkin, lit. "Arms Alchemy") is a manga series written and drawn by Nobuhiro Watsuki. Buso Renkin was serialized in Shueisha's shōnen magazine, Weekly Shōnen Jump from June 2003 to 2005, ending at 80 chapters. The individual chapters were collected by Shueisha into 10 tankōbon volumes which were released between January 5, 2004 and April 4, 2006. The series has been licensed by VIZ Media for US release and has been adapted into an anime by Xebec, which finished its run in Japan with a total of 26 episodes. There are also two drama CDs as well as a novel based on the series. On April 27, 2009, the series made its North American television debut on the FUNimation Channel.
The story begins when high school student Kazuki Muto is killed one night saving a mysterious girl from a monster, only to wake up in his school dorm, believing it to have been a dream. However, he soon finds out that dream wasn't a dream at all when a giant serpentine monster attacks him and his sister. Tokiko Tsumura, the girl he saved, explains that the monster is a homunculus. Kazuki had been attacked and killed by it when rescuing Tokiko. However she, feeling responsible for him, revived him by placing a Kakugane medallion in his chest, serving as a replacement heart.
The Kakugane, as Tokiko explains, is an alchemical (alchemistic) device that, when activated, takes a certain form based on the Kakugane's user, forming a unique Buso Renkin. The Buso Renkin is the only thing that can destroy a homunculus monster. Using this, Kazuki creates his own Buso Renkin, taking the form of a giant lance, later named 'Sunlight Heart'. Along with Tokiko and her own Buso Renkin (the Valkyrie Skirt, an execution scythe), Kazuki joins the fight against the homunculi and their master.