The story starts out with Kazuki trying to protect Tokiko from a homunculus (homunculus eat humans). When Kazuki dies, Tokiko places a kakugane medal in his chest that acts as his heart. The next moring Kazuki wakes up and thinks everything was a dream because he is still alive.
The kakugane is an alchemical device that when activated can give one the power to fight the homunculus monster.
Later Kazuki's sister gets attacked by the same homunculus monster that had attacked Tokiko. Tokiko shows up and explains to him how the homunculus is made by alchemy, and how he can use his kakugane medal to defeat the monster and that it's the only way to defeat a homunculus. In the end, Kazuki uses the kakugane medal and defeats the homunculus and saves his sister.
This seems like another good vs evil manga, and yet another boy finds or recieves special powers and uses them for good. I enjoy most stories with this plot or theme, though they seem to lack some orginality.
The first book itself somewhat bored me at first. But as I read more, I became more interested. Then I continued to read it again seriously. I suggest if you read the first manga, that you read it a few times before you decide whether or not you really like it.
I liked it and would recommend it for others to read. Though it is not my favorite, I enjoyed reading it nonetheless, and am sure others will too. ^_^