This is one of my more serious and critical reviews, not because I dislike yaoi or didn't like this OVA, but because I honestly REALLY did like it. Hybrid Child captivated me backwards, which honestly was a lot better than the other way around, like most anime does. (I'm not the type of person to sit through a show once I start it just because I feel like I need to...if something really bores me, I drop it.) The first part was interesting, no doubt...it set the story up and introduced the main concept that would be fleshed out during the subsequent parts. However, it wasn't what drew me in the continue watching. JUST the fact that there was plot was enough. I mean, that's literally the opposite of what the term "yaoi" stands for. The second part interested me twice as much as the first, despite the fact that I initally believed the two to be completely independent from each other. And, of course, parts 3 and 4 were the icing on the cake, and well awaited.
That being said, the sort of disconnect between the four different parts is what threw me off. I watched them all consecutively, and the time periods/characters in each part, though all closely connected, could easily confuse a first time watcher, which normally would be okay but I have a feeling it wasn't intentional (especially for a yaoi, which is normally designed so that the audience doesn't have to concentrate too much on details). Additionally, the premise that the plot had could have been extrapolated further. I personally thought the central idea, hybrid doll children that is, was a fantastic one, and maybe a 12 episode series could have better cultivated its potential. But it's a yaoi, whatareyagonnado. Not much more I could ask for. The fact that the plot itself was so well executed for an anime of this genre and length struck me as pretty incredible.
(Teetering between a rating of 7 and 8 due to the above stated reasons, I have decided on 7 because what does a number really mean, anyway?)
I recommend for any yaoi fan or anime fan that doesn't mind a bit of guy-on-guy action. There's also a bit of comedy thrown into the mix.