The manga has a great start with an interesting focus on "innocent devils", murderers who kill simply because it is the most optimal solution and thus, lacking an intent to kill. Quickly on, we are introduced to our two interesting main characters, and the cast continues to grow and... That's it.

Jumping right in, I have to say I adore the artwork. It's incredibly beautiful to look at, and the character designs, although a bit odd, are appealing and unique in their own ways. I especially adore how the artist draws each characters' eyes. Each character is distinguishable from the others, and the artist takes care not to reveal any gore or erotic content, despite all the heavy action. The pacing of the manga was decent; while it wasn't rushed by any means, I didn't feel compelled to turn the pages. The reason for this is the main characters.

Innocent Devil suffers from what I like to call "Twilight Syndrome", in which the supporting cast are all incredibly interesting and well-written, but the main cast is not. Touko Kamijou is a genius researcher who's studying innocent devils, but due to her childish appearance and nature, is not taken seriously by the academic society. We learn that she is very talkative about her research topic, but struggles at other conversations; and quite indecisive. That is all. Her character does not progress at all throughout the story, despite being a main character.

Akane Shinkai, on the other hand, is an innocent devil who kills her parents at a young age and is taken under the wing of Touko. A contrast to her guardian, Akane is mature and disciplined. We learn early on that she wishes to understand herself better, and grows to have a self vs self conflict between her child/innocent devil self, and the self who wishes to live normally as a non-devil. Akane's character is all laid out, and her personal conflict sets as one of the main driving forces of the story. Unfortunately, the author appears to have forgotten about it until the last second, where it's shoved in as a weak way to conclude the story.

Continuing on with the story, it's weak. Characters are introduced and given importance, and while we learn about these side characters, there is no real story for them to partake in. Each chapter feels relatively episodic, and the overall flow of the story is difficult to grasp. I am especially upset about Kanna Tousaki, who, despite being a very fascinating "morally gray" character, is thrown to be used as not only Touko's backstory material, but also the conclusion to Akane's long-time self-conflict.

Overall, a summary:
+ Great art
+ Interesting side characters
- Poor story
- Static and uninteresting main characters