Denpa Teki na Kanojo is not a bad anime, and perhaps I am being somewhat harsh with my scoring, but I cannot find it in myself to score it that much higher. Usually, I am a fan of OVA series. The length allows for a bit less focus on a single plot as in a movie, with a bit more focus than a longer series. At just two episodes long, however, Denpa Teki na Kanojo struggles to play to those strengths, and suffers as a result.
The premise, that a shy otaku-ish girl is convinced that a deliquent at her school was her King in a past life isn't awful. I've certainly heard worse. But it's really only used as the loosest of plot devices to ensure that the characters meet up. We don't explore their apparent past lives in any detail, and there's not enough interaction to convince the viewer that they are friends - partly due to a lack of time, but it leaves the dialogue between the two lead characters awkward and stilted. Moreover, the protagonist shares more meaningful lines with his 'servant's' sister, making their pairing feel that much more unbalanced.
The biggest problem that the show has, though, is that each episode is apparently unrelated and features such extreme violence and mental trauma that it cannot treat its themes properly. The extreme events that occur in each feel forced, and we aren't given enough time to know the characters who do give into the darker elements of their psyches. The result is that when something violent or shocking does happen, it's hard to care about - especially when it doesn't directly affect the main characters, however little we care about them either!
Denpa Teki na Kanojo would have been better drawn out into a 6 episode OVA, or a 12 episode series, or condensed into one film to focus on a single plot. Either way, there could have been more focus on the detective work that just seems to happen offscreen, and time to really watch the sanity of the antagonists unravel. As it is, the violence and gore seem hokey and cheap, mere excuses for lack of a deeper plot.