I just had to write a review for this because I really enjoyed this anime.
And for a change of pace, I'll break down this review to its components: Story, Art and animation, Sound and Overall enjoyment. (I don't do this normally and wanted to try it out)
Story= 8
Denpa Onna to Seishun Otoko deals on the mysterious and the unexplained. We have Touwa, Erio who has been missing for half a year and claims to have been abducted by aliens. But really, what actually happened while she was missing? What caused her to have amnesia? And then there's Niwa, Makoto, whose line of thinking depends on what can be seen and is proven, has to face these events.
Despite this serious-sounding background, this anime is quite far from being serious at all. Dealing with Erio's condition and helping her return to society as a normal Earthling is what Makoto is aiming for, while having to deal with some other things. I don't really think I've seen any anime with this plot, but I think it's actually pretty good.
Art/Animation= 10
I really liked the art for this anime. Its art is actually quite similar to the more recent Boku wa Tomodachi ga Sukunai (Which is another good anime I recommend) It's bright and very well-done. The animation (especially of that on the opening song) flows rather smoothly and deserves a perfect score on my review.
Sound= 10
The sound effects were unexpectedly good. The opening song didn't quite get to me at first, high and weird squeaky voice and all. But eventually, I came to like it and it's actually pretty catchy. The ending song, however, I didn't like as much. Voice acting is also good. No complaints there. The background music is what I'd like to point out, especially.
The music that plays sometimes in the background is outstanding and very well-done. It doesn't distract you from whatever is happening, and actually helps improve the setting of the scenes. Another perfect score there.
Overall= 9
Denpa Onna to Seishun Otoko would've been nice if it had more romance in it. Relationships between cousins are legal in Japan, right? Either way. despite not having an romantic elements in it, it's still a very enjoyable anime and I recommend watching it. No regrets guaranteed.