Kado: The Right Answer is a short anime series that takes alien invasion in a bit of an odd direction.
Kado starts with a giant cube-shaped alien artifact showing up on an airport runway and engulfing a jet and its passengers. Things progress from there through the usual panic, confusion, and eventually communication with an alien being (named Yaha-kui zaShunina). Over time, the plane passengers are all returned safely, but that's just the beginning of the alien encounter. Knowledge of huge scientific advancements follow, starting with unlimited clean energy, and quickly cause infighting among nations across the world. In the end, humanity has to deal with the zaShunina's real interests - I'm sure it's not much of a spoiler to say that it's not necessarily good for the humans involved.
The alien encounter here is framed as coming from higher dimensions, rather than life from elsewhere in our own universe. Not a new idea, but certainly less common than little green men or bugs or whatever from a distant star. The series uses some interesting visuals to emphasize the differences - for instance, zaShunina's arms aren't generally attached to his body and move independently, sometimes appearing and disappearing into thin air. There's also quite a lot of complex moving patterns used on the alien artifacts to give a sense of their strangeness and complexity.
Some of the usual themes in an alien encounter story are turned around in Kado. For instance, there's basically no secrecy involved - the media are fully involved at pretty much every step, at the insistence of zaShunina. He deals specifically with the government of Japan and shows no interest in other authorities, even when the United Nations gets involved. There's effectively no violence at all. The writers did a good job of making all these different themes work within the framework of an alien encounter.
This series moves along fairly slowly. It's only twelve episodes and about 4.5 hours long, and yet it still felt like the plot didn't progress much in places. I think the story could have fairly easily been put into a movie format rather than a series and been handled just as well. The extended time didn't bother me too much, though, since it gives the viewer some time to think about the various odd happenings.
The weakest part of Kado in my opinion is the ending. (Minor spoilers here but nothing too specific.) It turns out that zaShunina isn't the only alien being in the story, and in the end his plans are upset by cooperation between humans and that other alien. I thought the introduction of another non-human force felt contrived, coming into the story as late as it did. If they'd had some indication from the start that zaShunina wasn't alone, I think that would have worked a lot better.
Despite the weakness near the end, I had a fun time with Kado. Definitely not for the action lover or impatient viewer, but it brings up some interesting ideas and the production is excellent. Worth the short watch time if the concepts are at all interesting to you.