In the anime, the characters were either emofied or turned into pod people, their spines surgically removed, the main female turned into a mary sue, all the humor was siphooned out and the ending made no. fucking. sense. It was also a huuuuge downer. Pandora turned into glitter, Sizer opened the box and there was only a bird fossil in it - then suddenly Hamel started screaming and transforming into an even uglier demon form, and everyone was "Oh, he was possessed by the Demon King, the world is dooomed", and Flute just went and locked him in the box. Then it cut to ten years later, and Butler!Oboe was doing a voice over about how Flute would eventually break down and open the box in hopes of seeing Hamel again.
Meanwhile the fans are going "In the manga, this situation would have never come to pass, because the characters wouldn't have spent the last 9 chapters navelgazing - Sizer would not be so easily duped, Trom would not be so goddamn useless, Raiel would not have turned into a psycho, Flute would have never stood for locking Hamel in the box, and even if she had, she'd never be weak enough to open it again. I want my time back."
Seriously, it was so bad, the mangaka himself used some anime-related jokes in the manga. :/