An interesting universe, good artwork, and fun main characters make up for an unoriginal plot and uninspired bad guys.
Story: There are powerful demons in this universe that mimic diseases, but are really parasites, feeding off of their hosts until the host dies. To fight them, "dark doctors" use magical tomes. This story centers around two such doctors; one is a former swordsman seeking repentance, the other is his cute childhood friend that he has sworn to protect. They are looking for a special tome, with which they can put an end to all disease demons.
It's a clever universe, although the basic
outline of the plot is just Rurouni Kenshin with some minor adaptations.
Art: Excellent artwork. The characters are well-drawn (even if everyone looks very young), the fights are clear, and the demons are both intricate and interesting.
Character: The main characters are better than average, as are the various helpers they meet along the way. Each has an interesting back-story and adds something fun to the plot. The bad guys are really uninspired, though: overpowered, greedy, "I had a bad childhood, now I want the world to end!" types, pretty much without fail.
Enjoyment: Consistently a lot of fun. The manga is well-paced, it starts off with a bang, and it ends before becoming tedious.
Overall: A lot of fun. If you like Rurouni Kenshin, and similar manga, and are looking for something a bit shorter, this is a fun manga to read.