Deca-Dence is actually the mechanical world that they built for humanity. Because the surface is uninhabitable thanks to weird alien creatures. People are chosen to take on certain jobs at a certain age to help take care of and grow the mechanical world they live in. Our main character Natsume who has always dreamed of being a warrior gets stuck with cleaning duty.
The action sequences seem to be a little choppy but may even out over time. The art style is graphic without being gory. The writing, shading, and detail is especially intense. The world itself seems very interesting.
By interesting I mean meta. Being that the world that the human-looking people live in is a playable world by the chibi looking people. Our other main character, Kudarabi is asked to find bugs due to a cheat in the system that got somebody scrapped. He realizes that Natsume is a bug because she was declared dead so he in turn teaches her how to fight.
The opening is a banger.
The ending is a banger.
Well this took some serious competitive and anxiety heavy turns with very dramatic big twists so early in the show. I shouldn’t have expected any less from the animators of Attack on Titan. But in a much lighter sense, I would say this is a good anime to start with for noobs and pre-teens.