What's the line between imagination and reality. Should it be a pure fiction or should it be based on fact. what makes manga Detective Conan great is that Ayoma Gosho always consults his brothers who were chemists on technical aspect of crime scene investigation such as blood spatter and blood clot. So he didn't just make up the stories out of his pure imagination.
another case is slam dunk, The author Takehiko Inoue is a genuine basketball lover. He understands the game well, it can be seen on the lead Hanamichi Sakuragi who has the size and built big enough to actually play basketball in japan.He is not a make believe character that misled kids to think that physical strength is not required to excel at sport.
Now back to the manga

a young devil is eager to be a defense lawyer after watching court proceeding on TV
+art
The art is smoth and beautiful, and attention is paid for example. on the detail of Kucabara costume in his human form and his devil form. If fan service is what you are looking for in the manga, the girls are cute and some like Elimona is curvaceous.
+Kucabara and Bichura's transformation
Kucabara looks like a normal skinny teenager with no impressive physical feature that can wow a girl but he has a sympathetic personality and smile, bichura looks like a cudly plush toy. But by drinking a certain matter these two can revert to their original form.
Kucabara's is a gigantic muscular guy that can make Rob Gronkowskwi of NFL's New England patriot trembles in fear. While Bichura's real form is a cool winged humanoid demon.
-Really
The manga failed to present convincing and sound argument on each of the cases handled by kucabara. I don't want to give a spoiler but i guess the first case.
A punk is carrying a steel baseball bat, and riding his motorcyle on his way to help his buddies who are involved in a gang fight. He holds the steell bat on his right hand which is stretch wide and somehow he was distracted by something he accidently crushed the beautiful face of a high school girl with his steel bat. panicked he ran over an old woman. The punk was death and was sent to hell. Kucabara offered his service to the punk and set out to prove the innocence of his client
The problem lies first with the methode of investigation, at first Kucabara frantically searched for an evidence that can prove his client's innocence, leaving no single stone unturned . But as time runs out, Kucabara then used a tool that enable him to see the past.and just like that he found the evidence. problem is that where is all the excitement and fun if Kucabara can easily use magical tool to solve case. which means no need for thrilling investigation which is a good detective story is all about.
The second problem is in the real world, eventhough the punk didn't do it in purpose . The way he was holding the steel bat while speeding are sufficient grounds to punish him for carelesness that injures and kill people.
The fact that he was on his way to a fight means he bore an ill intention and had he not been killed in the accident he might would have killed someone in the fight.
It seems to me that the authors are ill prepared and didn't do research on the law and investigation techniques. They seem to be content with presenting their own interprestation of the event. Unfortunately people and even children now are exposed to law and investigation techniques through popular crime shows in television and some through law books. a high school freshman who at least watches crime show will wrinkle his forehead if she/he read this manga.
-Detective or action manga??
The combination didn't work well because sometimes enemy appears to disturb Kucabara's investigation, depriving us of how Kucabara's process the data and reach the conclussion. Or is it because the author didn't really understands how investigation works?
Reading Defense Devil

Judgement
The author should have at least spent times to read law book and consult police so that the manga could be more solid and not just imagination