Initially on my list of promising Spring shows -- on the grounds that it was Madhouse adapting a seinen manga -- this fell off the moment they announced the director. Same guy who turned the awesomely insane Nougami Neuro into a limp pile of unwatchable dullness.
A prison melodrama about bromantic bonds under cartoonishly oppressive guards, Rainbow mostly just embarrasses itself. I can see how all of this overwrought posturing could be pretty awesome in the hands of a capable director, but it just seems confused and inept here. He can't even commit to the tone heartily enough to make it hilarious.