after having seen this thing. I understand why the rating is so low. 20 minutes wasted on something that could be summed up in <spoiler>"they went to defeat the monster, they didn't make it and in the future they had more monsters" <spoiler>, part of the OVA is summed up in a attempt to empathize with characters without charisma. with a CGI that makes anyone throw up and a nasty animation that part of it is just the same shit repeated (when it's not stopped).
So far I haven't understood the motivation of the characters and the story itself. The anime is so empty that 50% is automatically forgotten from your mind because it doesn't matter at all.